1000 (number)

1000 or one thousand is the natural number following 999 and preceding 1001. In most English-speaking countries, it can be written with or without a comma or sometimes a period separating the thousands digit: 1,000.

A group of one thousand units is sometimes known, from Ancient Greek, as a chiliad.¹ A period of one thousand years may be known as a chiliad or, more often from Latin, as a millennium. The number 1000 is also sometimes described as a short thousand in medieval contexts where it is necessary to distinguish the Germanic concept of 1200 as a long thousand. It is the first 4-digit integer.

• The decimal representation for one thousand is
  • 1000—a one followed by three zeros, in the general notation;
  • 1 × 10³—in engineering notation, which for this number coincides with:
  • 1 × 10³ exactly—in scientific normalized exponential notation;
  • 1 E+3 exactly—in scientific E notation.
• The SI prefix for a thousand units is "kilo-", abbreviated to "k"—for instance, a kilogram or "kg" is a thousand grams. This is sometimes extended to non-SI contexts, such as "ka" (kiloannum) being used as a shorthand for periods of 1000 years. In computer science, however, "kilo-" is used more loosely to mean 2 to the 10th power (1024 or 2¹⁰).
• In the SI writing style, a non-breaking space can be used as a thousands separator, i.e., to separate the digits of a number at every power of 1000.
• Multiples of thousands are occasionally represented by replacing their last three zeros with the letter "K" or "k": for instance, writing "$30k" for $30,000 or using "Y2K" to denote the Year 2000 computer problem.
• A thousand units of currency, especially dollars or pounds, are colloquially called a grand. In the United States, this is sometimes abbreviated with a "G" suffix.

A chiliagon is a 1000-sided polygon.²

• 1001 = sphenic number (7 × 11 × 13), pentagonal number, pentatope number, palindromic number
• 1002 = sphenic number, Mertens function zero, abundant number, number of partitions of 22
• 1003 = the product of some prime p and the p^th prime, namely p = 17.
• 1004 = heptanacci number³
• 1005 = Mertens function zero, decagonal pyramidal number⁴
• 1006 = semiprime, product of two distinct isolated primes (2 and 503); unusual number; square-free number; number of compositions (ordered partitions) of 22 into squares; sum of two distinct pentatope numbers (5 and 1001); number of undirected Hamiltonian paths in 4 by 5 square grid graph;⁵ record gap between twin primes;⁶ number that is the sum of 7 positive 5th powers.⁷ In decimal: equidigital number; when turned around, the number looks like a prime, 9001; its cube can be concatenated from other cubes, 1_0_1_8_1_0_8_216 ("_" indicates concatenation, 0 = 0³, 1 = 1³, 8 = 2³, 216 = 6³)⁸
• 1007 = number that is the sum of 8 positive 5th powers⁹
• 1008 = divisible by the number of primes below it
• 1009 = smallest four-digit prime, palindromic in bases 11, 15, 19, 24 and 28: (838₁₁, 474₁₅, 2F2₁₉, 1I1₂₄, 181₂₈). It is also a Lucky prime and Chen prime.
• 1010 = 10³ + 10,¹⁰ Mertens function zero
• 1011 = the largest n such that 2ⁿ contains 101 and does not contain 11011, Harshad number in bases 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 (and 202 other bases), number of partitions of 1 into reciprocals of positive integers <= 16 Egyptian fraction¹¹
• 1012 = ternary number, (32₁₀) quadruple triangular number (triangular number is 253),¹² number of partitions of 1 into reciprocals of positive integers <= 17 Egyptian fraction¹¹
• 1013 = Sophie Germain prime,¹³ centered square number,¹⁴ Mertens function zero
• 1014 = 2¹⁰-10,¹⁵ Mertens function zero, sum of the nontriangular numbers between successive triangular numbers 78 and 91¹⁶
• 1015 = square pyramidal number¹⁷
• 1016 = member of the Mian–Chowla sequence,¹⁸ stella octangula number, number of surface points on a cube with edge-length 14¹⁹
• 1017 = generalized triacontagonal number²⁰
• 1018 = Mertens function zero, 1018¹⁶ + 1 is prime²¹
• 1019 = Sophie Germain prime,¹³ safe prime,²² Chen prime
• 1020 = polydivisible number
• 1021 = twin prime with 1019. It is also a Lucky prime.
• 1022 = Friedman number
• 1023 = sum of five consecutive primes (193 + 197 + 199 + 211 + 223);²³ the number of three-dimensional polycubes with 7 cells;²⁴ number of elements in a 9-simplex; highest number one can count to on one's fingers using binary; magic number used in Global Positioning System signals.
• 1024 = 32² = 4⁵ = 2¹⁰, the number of bytes in a kilobyte (in 1999, the IEC coined kibibyte to use for 1024 with kilobyte being 1000, but this convention has not been widely adopted). 1024 is the smallest 4-digit square and also a Friedman number.
• 1025 = Proth number 2¹⁰ + 1; member of Moser–de Bruijn sequence, because its base-4 representation (100001₄) contains only digits 0 and 1, or it's a sum of distinct powers of 4 (4⁵ + 4⁰); Jacobsthal-Lucas number; hypotenuse of primitive Pythagorean triangle
• 1026 = sum of two distinct powers of 2 (1024 + 2)
• 1027 = sum of the squares of the first eight primes; can be written from base 2 to base 18 using only the digits 0 to 9.
• 1028 = sum of totient function for first 58 integers; can be written from base 2 to base 18 using only the digits 0 to 9; number of primes <= 2¹³.²⁵
• 1029 = can be written from base 2 to base 18 using only the digits 0 to 9.
• 1030 = generalized heptagonal number
• 1031 = exponent and number of ones for the fifth base-10 repunit prime,²⁶ Sophie Germain prime,¹³ super-prime, Chen prime
• 1032 = sum of two distinct powers of 2 (1024 + 8)
• 1033 = emirp, twin prime with 1031
• 1034 = sum of 12 positive 9th powers²⁷
• 1035 = 45th triangular number,²⁸ hexagonal number²⁹
• 1036 = central polygonal number³⁰
• 1037 = number in E-toothpick sequence³¹
• 1038 = even integer that is an unordered sum of two primes in exactly 40 ways³²
• 1039 = prime of the form 8n+7,³³ number of partitions of 30 that do not contain 1 as a part,³⁴ Chen prime, Lucky prime
• 1040 = 4⁵ + 4²: sum of distinct powers of 4.³⁵ The number of pieces that could be seen in a 6 × 6 × 6× 6 Rubik's Tesseract.
• 1041 = sum of 11 positive 5th powers³⁶
• 1042 = sum of 12 positive 5th powers³⁷
• 1043 = number whose sum of even digits and sum of odd digits are even³⁸
• 1044 = sum of distinct powers of 4³⁵
• 1045 = octagonal number³⁹
• 1046 = coefficient of f(q) (3rd order mock theta function)⁴⁰
• 1047 = number of ways to split a strict composition of 18 into contiguous subsequences that have the same sum⁴¹
• 1048 = number of partitions of 27 into squarefree parts⁴²
• 1049 = Sophie Germain prime,¹³ highly cototient number,⁴³ Chen prime
• 1050 = 1050₈ to decimal becomes a pronic number (552₁₀),⁴⁴ number of parts in all partitions of 29 into distinct parts⁴⁵
• 1051 = centered pentagonal number,⁴⁶ centered decagonal number
• 1052 = sum of 9 positive 6th powers⁴⁷
• 1053 = triangular matchstick number⁴⁸
• 1054 = centered triangular number⁴⁹
• 1055 = sum of 12 positive 6th powers⁵⁰
• 1056 = pronic number⁵¹
• 1057 = central polygonal number⁵²
• 1058 = sum of 4 positive 5th powers,⁵³ area of a square with diagonal 46⁵⁴
• 1059 = number n such that n⁴ is written in the form of a sum of four positive 4th powers⁵⁵
• 1060 = sum of the first twenty-five primes from 2 through 97 (the number of primes less than 100),⁵⁶ and sixth sum of 10 consecutive primes, starting with 23 through 131.⁵⁷
• 1061 = emirp, twin prime with 1063, number of prime numbers between 1000 and 10000 (or, number of four-digit primes in decimal representation)⁵⁸
• 1062 = number that is not the sum of two palindromes⁵⁹
• 1063 = super-prime, sum of seven consecutive primes (137 + 139 + 149 + 151 + 157 + 163 + 167); near-wall-sun-sun prime.⁶⁰ It is also a twin prime with 1061.
• 1064 = sum of two positive cubes⁶¹
• 1065 = generalized duodecagonal⁶²
• 1066 = number whose sum of their divisors is a square⁶³
• 1067 = number of strict integer partitions of 45 in which are empty or have smallest part not dividing the other ones⁶⁴
• 1068 = number that is the sum of 7 positive 5th powers,⁷ total number of parts in all partitions of 15⁶⁵
• 1069 = emirp⁶⁶
• 1070 = number that is the sum of 9 positive 5th powers⁶⁷
• 1071 = heptagonal number⁶⁸
• 1072 = centered heptagonal number⁶⁹
• 1073 = number that is the sum of 12 positive 5th powers³⁷
• 1074 = number that is not the sum of two palindromes⁵⁹
• 1075 = number non-sum of two palindromes⁵⁹
• 1076 = number of strict trees weight 11⁷⁰
• 1077 = number where 7 outnumbers every other digit in the number⁷¹
• 1078 = Euler transform of negative integers⁷²
• 1079 = every positive integer is the sum of at most 1079 tenth powers.
• 1080 = pentagonal number,⁷³ largely composite number⁷⁴
• 1081 = 46th triangular number,²⁸ member of Padovan sequence⁷⁵
• 1082 = central polygonal number³⁰
• 1083 = three-quarter square,⁷⁶ number of partitions of 53 into prime parts⁷⁷
• 1084 = third spoke of a hexagonal spiral,⁷⁸ 1084⁶⁴ + 1 is prime
• 1085 = number of partitions of n into distinct parts > or = 2⁷⁹
• 1086 = Smith number,⁸⁰ sum of totient function for first 59 integers
• 1087 = super-prime, cousin prime, lucky prime⁸¹
• 1088 = octo-triangular number, (triangular number result being 136)⁸² sum of two distinct powers of 2, (1024 + 64)⁸³ number that is divisible by exactly seven primes with the inclusion of multiplicity⁸⁴
• 1089 = 33², nonagonal number, centered octagonal number, first natural number whose digits in its decimal representation get reversed when multiplied by 9.⁸⁵
• 1090 = sum of 5 positive 5th powers⁸⁶
• 1091 = cousin prime and twin prime with 1093
• 1092 = divisible by the number of primes below it
• 1093 = the smallest Wieferich prime (the only other known Wieferich prime is 3511⁸⁷), twin prime with 1091 and star number⁸⁸
• 1094 = sum of 9 positive 5th powers,⁶⁷ 1094⁶⁴ + 1 is prime
• 1095 = sum of 10 positive 5th powers,⁸⁹ number that is not the sum of two palindromes
• 1096 = hendecagonal number,⁹⁰ number of strict solid partitions of 18⁹¹
• 1097 = emirp,⁶⁶ Chen prime
• 1098 = multiple of 9 containing digit 9 in its base-10 representation⁹²
• 1099 = number where 9 outnumbers every other digit⁹³

• 1100 = number of partitions of 61 into distinct squarefree parts⁹⁴
• 1101 = pinwheel number⁹⁵
• 1102 = sum of totient function for first 60 integers
• 1103 = Sophie Germain prime,¹³ balanced prime⁹⁶
• 1104 = Keith number⁹⁷
• 1105 = 33² + 4² = 32² + 9² = 31² + 12² = 23² + 24², Carmichael number,⁹⁸ magic constant of n × n normal magic square and n-queens problem for n = 13, decagonal number,⁹⁹ centered square number,¹⁴ Fermat pseudoprime¹⁰⁰
• 1106 = number of regions into which the plane is divided when drawing 24 ellipses¹⁰¹
• 1107 = number of non-isomorphic strict T₀ multiset partitions of weight 8¹⁰²
• 1108 = number k such that k⁶⁴ + 1 is prime
• 1109 = Friedlander-Iwaniec prime,¹⁰³ Chen prime
• 1110 = k such that 2^k + 3 is prime¹⁰⁴
• 1111 = 11 × 101, palindrome that is a product of two palindromic primes,¹⁰⁵ repunit¹⁰⁶
• 1112 = k such that 9^k - 2 is a prime¹⁰⁷
• 1113 = number of strict partions of 40¹⁰⁸
• 1114 = number of ways to write 22 as an orderless product of orderless sums¹⁰⁹
• 1115 = number of partitions of 27 into a prime number of parts¹¹⁰
• 1116 = divisible by the number of primes below it
• 1117 = number of diagonally symmetric polyominoes with 16 cells,¹¹¹ Chen prime
• 1118 = number of unimodular 2 × 2 matrices having all terms in {0,1,...,21}¹¹²
• 1119 = number of bipartite graphs with 9 nodes¹¹³
• 1120 = number k such that k⁶⁴ + 1 is prime
• 1121 = number of squares between 34² and 34⁴.¹¹⁴
• 1122 = pronic number,⁵¹ divisible by the number of primes below it
• 1123 = balanced prime⁹⁶
• 1124 = Leyland number¹¹⁵ using 2 & 10 (2¹⁰ + 10²), spy number
• 1125 = Achilles number
• 1126 = number of 2 × 2 non-singular integer matrices with entries from {0, 1, 2, 3, 4, 5}¹¹⁶
• 1127 = maximal number of pieces that can be obtained by cutting an annulus with 46 cuts¹¹⁷
• 1128 = 47th triangular number,²⁸ 24th hexagonal number,²⁹ divisible by the number of primes below it (188 × 6).¹¹⁸ 1128 is the dimensional representation of the largest vertex operator algebra with central charge of 24, D₂₄.¹¹⁹
• 1129 = number of lattice points inside a circle of radius 19¹²⁰
• 1130 = skiponacci number¹²¹
• 1131 = number of edges in the hexagonal triangle T(26)¹²²
• 1132 = number of simple unlabeled graphs with 9 nodes of 2 colors whose components are complete graphs¹²³
• 1133 = number of primitive subsequences of {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}¹²⁴
• 1134 = divisible by the number of primes below it, triangular matchstick number⁴⁸
• 1135 = centered triangular number¹²⁵
• 1136 = number of independent vertex sets and vertex covers in the 7-sunlet graph¹²⁶
• 1137 = sum of values of vertices at level 5 of the hyperbolic Pascal pyramid¹²⁷
• 1138 = recurring number in the works of George Lucas and his companies, beginning with his first feature film – THX 1138; particularly, a special code for Easter eggs on Star Wars DVDs.
• 1139 = wiener index of the windmill graph D(3,17)¹²⁸
• 1140 = tetrahedral number¹²⁹
• 1141 = 7-Knödel number¹³⁰
• 1142 = n such that n³² + 1 is prime,¹³¹ spy number
• 1143 = number of set partitions of 8 elements with 2 connectors¹³²
• 1144 is not the sum of a pair of twin primes¹³³
• 1145 = 5-Knödel number¹³⁴
• 1146 is not the sum of a pair of twin primes¹³³
• 1147 = 31 × 37 (a product of 2 successive primes)¹³⁵
• 1148 is not the sum of a pair of twin primes¹³³
• 1149 = a product of two palindromic primes¹³⁶
• 1150 = number of 11-iamonds without bilateral symmetry.¹³⁷
• 1151 = first prime following a prime gap of 22,¹³⁸ Chen prime
• 1152 = highly totient number,¹³⁹ 3-smooth number (2⁷×3²), area of a square with diagonal 48,⁵⁴ Achilles number
• 1153 = super-prime, Proth prime¹⁴⁰
• 1154 = 2 × 24² + 2 = number of points on surface of tetrahedron with edge length 24¹⁴¹
• 1155 = number of edges in the join of two cycle graphs, both of order 33,¹⁴² product of first four odd primes (3*5*7*11)
• 1156 = 34², octahedral number,¹⁴³ centered pentagonal number,⁴⁶ centered hendecagonal number.¹⁴⁴
• 1157 = smallest number that can be written as n^2+1 without any prime factors that can be written as a^2+1.¹⁴⁵
• 1158 = number of points on surface of octahedron with edge length 17¹⁴⁶
• 1159 = member of the Mian–Chowla sequence,¹⁸ a centered octahedral number¹⁴⁷
• 1160 = octagonal number¹⁴⁸
• 1161 = sum of the first twenty-six primes
• 1162 = pentagonal number,⁷³ sum of totient function for first 61 integers
• 1163 = smallest prime > 34².¹⁴⁹ See Legendre's conjecture. Chen prime.
• 1164 = number of chains of multisets that partition a normal multiset of weight 8, where a multiset is normal if it spans an initial interval of positive integers¹⁵⁰
• 1165 = 5-Knödel number¹³⁴
• 1166 = heptagonal pyramidal number¹⁵¹
• 1167 = number of rational numbers which can be constructed from the set of integers between 1 and 43¹⁵²
• 1168 = antisigma(49)¹⁵³
• 1169 = highly cototient number⁴³
• 1170 = highest possible score in a National Academic Quiz Tournaments (NAQT) match
• 1171 = super-prime
• 1172 = number of subsets of first 14 integers that have a sum divisible by 14¹⁵⁴
• 1173 = number of simple triangulation on a plane with 9 nodes¹⁵⁵
• 1174 = number of widely totally strongly normal compositions of 16
• 1175 = maximal number of pieces that can be obtained by cutting an annulus with 47 cuts¹¹⁷
• 1176 = 48th triangular number²⁸
• 1177 = heptagonal number⁶⁸
• 1178 = number of surface points on a cube with edge-length 15¹⁹
• 1179 = number of different permanents of binary 7*7 matrices¹⁵⁶
• 1180 = smallest number of non-integral partitions into non-integral power >1000.¹⁵⁷
• 1181 = smallest k over 1000 such that 8*10^k-49 is prime.¹⁵⁸
• 1182 = number of necklaces possible with 14 beads of 2 colors (that cannot be turned over)¹⁵⁹
• 1183 = pentagonal pyramidal number
• 1184 = amicable number with 1210¹⁶⁰
• 1185 = number of partitions of 45 into pairwise relatively prime parts¹⁶¹
• 1186 = number of diagonally symmetric polyominoes with 15 cells,¹¹¹ number of partitions of 54 into prime parts
• 1187 = safe prime,²² Stern prime,¹⁶² balanced prime,⁹⁶ Chen prime
• 1188 = first 4 digit multiple of 18 to contain 18¹⁶³
• 1189 = number of squares between 35² and 35⁴.¹¹⁴
• 1190 = pronic number,⁵¹ number of cards to build a 28-tier house of cards¹⁶⁴
• 1191 = 35² - 35 + 1 = H₃₅ (the 35th Hogben number)¹⁶⁵
• 1192 = sum of totient function for first 62 integers
• 1193 = a number such that 4¹¹⁹³ - 3¹¹⁹³ is prime, Chen prime
• 1194 = number of permutations that can be reached with 8 moves of 2 bishops and 1 rook on a 3 × 3 chessboard¹⁶⁶
• 1195 = smallest four-digit number for which a⁻¹(n) is an integer is a(n) is 2*a(n-1) - (-1)ⁿ¹⁶⁷
• 1196 = ${\displaystyle \sum _{k=1}^{38}\sigma (k)}$¹⁶⁸
• 1197 = pinwheel number⁹⁵
• 1198 = centered heptagonal number⁶⁹
• 1199 = area of the 20th conjoined trapezoid¹⁶⁹

• 1200 = the long thousand, ten "long hundreds" of 120 each, the traditional reckoning of large numbers in Germanic languages, the number of households the Nielsen ratings sample,¹⁷⁰ number k such that k⁶⁴ + 1 is prime
• 1201 = centered square number,¹⁴ super-prime, centered decagonal number
• 1202 = number of regions the plane is divided into by 25 ellipses¹⁰¹
• 1203: first 4 digit number in the coordinating sequence for the (2,6,∞) tiling of the hyperbolic plane¹⁷¹
• 1204: magic constant of a 7 × 7 × 7 magic cube¹⁷²
• 1205 = number of partitions of 28 such that the number of odd parts is a part¹⁷³
• 1206 = 29-gonal number ¹⁷⁴
• 1207 = composite de Polignac number¹⁷⁵
• 1208 = number of strict chains of divisors starting with the superprimorial A006939(3)¹⁷⁶
• 1209 = The product of all ordered non-empty subsets of {3,1} if {a,b} is a||b: 1209=1*3*13*31
• 1210 = amicable number with 1184;¹⁷⁷ Self-descriptive number.
• 1211 = composite de Polignac number¹⁷⁵
• 1212 = ${\displaystyle \sum _{k=0}^{17}p(k)}$, where ${\displaystyle p}$ is the number of partions of ${\displaystyle k}$¹⁷⁸
• 1213 = emirp
• 1214 = sum of first 39 composite numbers,¹⁷⁹ spy number
• 1215 = number of edges in the hexagonal triangle T(27)¹²²
• 1216 = nonagonal number¹⁸⁰
• 1217 = super-prime, Proth prime¹⁴⁰
• 1218 = triangular matchstick number⁴⁸
• 1219 = Mertens function zero, centered triangular number¹²⁵
• 1220 = Mertens function zero, number of binary vectors of length 16 containing no singletons¹⁸¹
• 1221 = product of the first two digit, and three digit repdigit
• 1222 = hexagonal pyramidal number
• 1223 = Sophie Germain prime,¹³ balanced prime, 200th prime number⁹⁶
• 1224 = number of edges in the join of two cycle graphs, both of order 34¹⁴²
• 1225 = 35², 49th triangular number,²⁸ 2nd nontrivial square triangular number,¹⁸² 25th hexagonal number,²⁹ and the smallest number >1 to be all three.¹⁸³ Additionally a centered octagonal number,¹⁸⁴ icosienneagonal,¹⁸⁵ hexacontagonal,¹⁸⁶ and hecatonicositetragonal (124-gonal) number, and the sum of 5 consecutive odd cubes (1³ + 3³ + 5³ + 7³ + 9³)
• 1226 = number of rooted identity trees with 15 nodes ¹⁸⁷
• 1227 = smallest number representable as the sum of 3 triangular numbers in 27 ways¹⁸⁸
• 1228 = sum of totient function for first 63 integers
• 1229 = Sophie Germain prime,¹³ number of primes under 10,000, emirp
• 1230 = the Mahonian number: T(9, 6)¹⁸⁹
• 1231 = smallest mountain emirp, as 121, smallest mountain number is 11 × 11
• 1232 = number of labeled ordered set of partitions of a 7-set into odd parts¹⁹⁰
• 1233 = 12² + 33²
• 1234 = number of parts in all partitions of 30 into distinct parts,⁴⁵ smallest whole number containing all numbers from 1 to 4
• 1235 = excluding duplicates, contains the first four Fibonacci numbers ¹⁹¹
• 1236 = 617 + 619: sum of twin prime pair¹⁹²
• 1237 = prime of the form 2p-1
• 1238 = number of partitions of 31 that do not contain 1 as a part³⁴
• 1239 = toothpick number in 3D¹⁹³
• 1240 = square pyramidal number¹⁷
• 1241 = centered cube number,¹⁹⁴ spy number
• 1242 = decagonal number⁹⁹
• 1243 = composite de Polignac number¹⁷⁵
• 1244 = number of complete partitions of 25¹⁹⁵
• 1245 = Number of labeled spanning intersecting set-systems on 5 vertices.¹⁹⁶
• 1246 = number of partitions of 38 such that no part occurs more than once¹⁹⁷
• 1247 = pentagonal number⁷³
• 1248 = the first four powers of 2 concatenated together
• 1249 = emirp, trimorphic number¹⁹⁸
• 1250 = area of a square with diagonal 50⁵⁴
• 1251 = 2 × 25² + 1 = number of different 2 × 2 determinants with integer entries from 0 to 25¹⁹⁹
• 1252 = 2 × 25² + 2 = number of points on surface of tetrahedron with edgelength 25¹⁴¹
• 1253 = number of partitions of 23 with at least one distinct part²⁰⁰
• 1254 = number of partitions of 23 into relatively prime parts²⁰¹
• 1255 = Mertens function zero, number of ways to write 23 as an orderless product of orderless sums,¹⁰⁹ number of partitions of 23²⁰²
• 1256 = 1 × 2 × (5²)² + 6,²⁰³ Mertens function zero
• 1257 = number of lattice points inside a circle of radius 20¹²⁰
• 1258 = 1 × 2 × (5²)² + 8,²⁰³ Mertens function zero
• 1259 = highly cototient number⁴³
• 1260 = the 16th highly composite number,²⁰⁴ pronic number,⁵¹ the smallest vampire number,²⁰⁵ sum of totient function for first 64 integers, number of strict partions of 41¹⁰⁸ and appears twice in the Book of Revelation
• 1261 = star number,⁸⁸ Mertens function zero
• 1262 = maximal number of regions the plane is divided into by drawing 36 circles²⁰⁶
• 1263 = rounded total surface area of a regular tetrahedron with edge length 27²⁰⁷
• 1264 = sum of the first 27 primes
• 1265 = number of rooted trees with 43 vertices in which vertices at the same level have the same degree²⁰⁸
• 1266 = centered pentagonal number,⁴⁶ Mertens function zero
• 1267 = 7-Knödel number¹³⁰
• 1268 = number of partitions of 37 into prime power parts²⁰⁹
• 1269 = least number of triangles of the Spiral of Theodorus to complete 11 revolutions²¹⁰
• 1270 = 25 + 24×26 + 23×27,²¹¹ Mertens function zero
• 1271 = sum of first 40 composite numbers¹⁷⁹
• 1272 = sum of first 41 nonprimes²¹²
• 1273 = 19 × 67 = 19 × prime(19)²¹³
• 1274 = sum of the nontriangular numbers between successive triangular numbers
• 1275 = 50th triangular number,²⁸ equivalently the sum of the first 50 natural numbers
• 1276 = number of irredundant sets in the 25-cocktail party graph²¹⁴
• 1277 = the start of a prime constellation of length 9 (a "prime nonuple")
• 1278 = number of Narayana's cows and calves after 20 years²¹⁵
• 1279 = Mertens function zero, Mersenne prime exponent
• 1280 = Mertens function zero, number of parts in all compositions of 9²¹⁶
• 1281 = octagonal number¹⁴⁸
• 1282 = Mertens function zero, number of partitions of 46 into pairwise relatively prime parts¹⁶¹
• 1283 = safe prime²²
• 1284 = 641 + 643: sum of twin prime pair¹⁹²
• 1285 = Mertens function zero, number of free nonominoes, number of parallelogram polyominoes with 10 cells.²¹⁷
• 1286 = number of inequivalent connected planar figures that can be formed from five 1 X 2 rectangles (or dominoes) such that each pair of touching rectangles shares exactly one edge, of length 1, and the adjacency graph of the rectangles is a tree²¹⁸
• 1287 = ${\displaystyle {13 \choose 5}}$²¹⁹
• 1288 = heptagonal number⁶⁸
• 1289 = Sophie Germain prime,¹³ Mertens function zero
• 1290 = ${\displaystyle {\frac {1289+1291}{2}}}$, average of a twin prime pair²²⁰
• 1291 = largest prime < 6⁴,²²¹ Mertens function zero
• 1292 = number such that phi(1292) = phi(sigma(1292)),²²² Mertens function zero
• 1293 = ${\displaystyle \sum _{j=1}^{n}j\times prime(j)}$²²³
• 1294 = rounded volume of a regular octahedron with edge length 14²²⁴
• 1295 = number of edges in the join of two cycle graphs, both of order 35¹⁴²
• 1296 = 36² = 6⁴, sum of the cubes of the first eight positive integers, the number of rectangles on a normal 8 × 8 chessboard, also the maximum font size allowed in Adobe InDesign, number of combinations of 2 characters(00-ZZ)
• 1297 = super-prime, Mertens function zero, pinwheel number⁹⁵
• 1298 = number of partitions of 55 into prime parts
• 1299 = Mertens function zero, number of partitions of 52 such that the smallest part is greater than or equal to number of parts²²⁵

• 1300 = Sum of the first 4 fifth powers, Mertens function zero, largest possible win margin in an NAQT match; smallest even odd-factor hyperperfect number
• 1301 = centered square number,¹⁴ Honaker prime,²²⁶ number of trees with 13 unlabeled nodes²²⁷
• 1302 = Mertens function zero, number of edges in the hexagonal triangle T(28)¹²²
• 1303 = prime of form 21n+1 and 31n+1²²⁸²²⁹
• 1304 = sum of 1304₆ and 1304 ₉ which is 328+976
• 1305 = triangular matchstick number⁴⁸
• 1306 = Mertens function zero. In base 10, raising the digits of 1306 to powers of successive integers equals itself: 1306 = 1¹ + 3² + 0³ + 6⁴. 135, 175, 518, and 598 also have this property. Centered triangular number.¹²⁵
• 1307 = safe prime²²
• 1308 = sum of totient function for first 65 integers
• 1309 = the first sphenic number followed by two consecutive such number
• 1310 = smallest number in the middle of a set of three sphenic numbers
• 1311 = number of integer partitions of 32 with no part dividing all the others²³⁰
• 1312 = member of the Mian-Chowla sequence;¹⁸
• 1313 = sum of all parts of all partitions of 14 ²³¹
• 1314 = number of integer partitions of 41 whose distinct parts are connected²³²
• 1315 = 10^(2n+1)-7*10^n-1 is prime.²³³
• 1316 = Euler transformation of sigma(11)²³⁴
• 1317 = 1317 Only odd four digit number to divide the concatenation of all number up to itself in base 25²³⁵
• 1318⁵¹² + 1 is prime,²³⁶ Mertens function zero
• 1319 = safe prime²²
• 1320 = 659 + 661: sum of twin prime pair¹⁹²
• 1321 = Friedlander-Iwaniec prime¹⁰³
• 1322 = area of the 21st conjoined trapezoid¹⁶⁹
• 1323 = Achilles number
• 1324 = if D(n) is the nth representation of 1, 2 arranged lexicographically. 1324 is the first non-1 number which is D(D(x))²³⁷
• 1325 = Markov number,²³⁸ centered tetrahedral number²³⁹
• 1326 = 51st triangular number,²⁸ hexagonal number,²⁹ Mertens function zero
• 1327 = first prime followed by 33 consecutive composite numbers
• 1328 = sum of totient function for first 66 integers
• 1329 = Mertens function zero, sum of first 41 composite numbers¹⁷⁹
• 1330 = tetrahedral number,¹²⁹ forms a Ruth–Aaron pair with 1331 under second definition
• 1331 = 11³, centered heptagonal number,⁶⁹ forms a Ruth–Aaron pair with 1330 under second definition. This is the only non-trivial cube of the form x² + x − 1, for x = 36.
• 1332 = pronic number⁵¹
• 1333 = 37² - 37 + 1 = H₃₇ (the 37th Hogben number)¹⁶⁵
• 1334 = maximal number of regions the plane is divided into by drawing 37 circles²⁰⁶
• 1335 = pentagonal number,⁷³ Mertens function zero
• 1336 = sum of gcd(x, y) for 1 <= x, y <= 24,²⁴⁰ Mertens function zero
• 1337 = Used in the novel form of spelling called leet. Approximate melting point of gold in kelvins.
• 1338 = atomic number of the noble element of period 18,²⁴¹ Mertens function zero
• 1339 = First 4 digit number to appear twice in the sequence of sum of cubes of primes dividing n²⁴²
• 1340 = k such that 5 × 2^k - 1 is prime²⁴³
• 1341 = First mountain number with 2 jumps of more than one.
• 1342 = ${\displaystyle \sum _{k=1}^{40}\sigma (k)}$,¹⁶⁸ Mertens function zero
• 1343 = cropped hexagone²⁴⁴
• 1344 = 37² - 5², the only way to express 1344 as a difference of prime squares²⁴⁵
• 1345 = k such that k, k+1 and k+2 are products of two primes²⁴⁶
• 1346 = number of locally disjointed rooted trees with 10 nodes²⁴⁷
• 1347 = concatenation of first 4 Lucas numbers ²⁴⁸
• 1348 = number of ways to stack 22 pennies such that every penny is in a stack of one or two²⁴⁹
• 1349 = Stern-Jacobsthal number²⁵⁰
• 1350 = nonagonal number¹⁸⁰
• 1351 = number of partitions of 28 into a prime number of parts¹¹⁰
• 1352 = number of surface points on a cube with edge-length 16,¹⁹ Achilles number
• 1353 = 2 × 26² + 1 = number of different 2 × 2 determinants with integer entries from 0 to 26¹⁹⁹
• 1354 = 2 × 26² + 2 = number of points on surface of tetrahedron with edgelength 26¹⁴¹
• 1355 appears for the first time in the Recamán's sequence at n = 325,374,625,245.²⁵¹ Or in other words A057167(1355) = 325,374,625,245²⁵²²⁵³
• 1356 is not the sum of a pair of twin primes¹³³
• 1357 = number of nonnegative solutions to x² + y² ≤ 41²²⁵⁴
• 1358 = rounded total surface area of a regular tetrahedron with edge length 28²⁰⁷
• 1359 is the 42d term of Flavius Josephus's sieve²⁵⁵
• 1360 = 37² - 3², the only way to express 1360 as a difference of prime squares²⁴⁵
• 1361 = first prime following a prime gap of 34,¹³⁸ centered decagonal number, 3rd Mills' prime, Honaker prime²²⁶
• 1362 = number of achiral integer partitions of 48²⁵⁶
• 1363 = the number of ways to modify a circular arrangement of 14 objects by swapping one or more adjacent pairs²⁵⁷
• 1364 = Lucas number²⁵⁸
• 1365 = pentatope number²⁵⁹
• 1366 = Arima number, after Yoriyuki Arima who in 1769 constructed this sequence as the number of moves of the outer ring in the optimal solution for the Chinese Rings puzzle²⁶⁰
• 1367 = safe prime,²² balanced prime, sum of three, nine, and eleven consecutive primes (449 + 457 + 461, 131 + 137 + 139 + 149 + 151 + 157 + 163 + 167 + 173, and 101 + 103 + 107 + 109 + 113 + 127 + 131 + 137 + 139 + 149 + 151),⁹⁶
• 1368 = number of edges in the join of two cycle graphs, both of order 36¹⁴²
• 1369 = 37², centered octagonal number¹⁸⁴
• 1370 = σ₂(37): sum of squares of divisors of 37²⁶¹
• 1371 = sum of the first 28 primes
• 1372 = Achilles number
• 1373 = number of lattice points inside a circle of radius 21¹²⁰
• 1374 = number of unimodular 2 × 2 matrices having all terms in {0,1,...,23}¹¹²
• 1375 = decagonal pyramidal number⁴
• 1376 = primitive abundant number (abundant number all of whose proper divisors are deficient numbers)²⁶²
• 1377 = maximal number of pieces that can be obtained by cutting an annulus with 51 cuts¹¹⁷
• 1378 = 52nd triangular number²⁸
• 1379 = magic constant of n × n normal magic square and n-queens problem for n = 14.
• 1380 = number of 8-step mappings with 4 inputs²⁶³
• 1381 = centered pentagonal number⁴⁶ Mertens function zero
• 1382 = first 4 digit tetrachi number ²⁶⁴
• 1383 = 3 × 461. 10¹³⁸³ + 7 is prime²⁶⁵
• 1384 = ${\displaystyle \sum _{k=1}^{41}\sigma (k)}$¹⁶⁸
• 1385 = up/down number²⁶⁶
• 1386 = octagonal pyramidal number²⁶⁷
• 1387 = 5th Fermat pseudoprime of base 2,²⁶⁸ 22nd centered hexagonal number and the 19th decagonal number,⁹⁹ second Super-Poulet number.²⁶⁹
• 1388 = 4 × 19² - 3 × 19 + 1 and is therefore on the x-axis of Ulams spiral²⁷⁰
• 1389 = sum of first 42 composite numbers¹⁷⁹
• 1390 = sum of first 43 nonprimes²¹²
• 1391 = number of rational numbers which can be constructed from the set of integers between 1 and 47¹⁵²
• 1392 = number of edges in the hexagonal triangle T(29)¹²²
• 1393 = 7-Knödel number¹³⁰
• 1394 = sum of totient function for first 67 integers
• 1395 = vampire number,²⁰⁵ member of the Mian–Chowla sequence¹⁸ triangular matchstick number⁴⁸
• 1396 = centered triangular number¹²⁵
• 1397 = ${\displaystyle \left\lfloor 5^{\frac {9}{2}}\right\rfloor }$²⁷¹
• 1398 = number of integer partitions of 40 whose distinct parts are connected²³²
• 1399 = emirp²⁷²

• 1400 = number of sum-free subsets of {1, ..., 15}²⁷³
• 1401 = pinwheel number⁹⁵
• 1402 = number of integer partitions of 48 whose augmented differences are distinct,²⁷⁴ number of signed trees with 8 nodes²⁷⁵
• 1403 = smallest x such that M(x) = 11, where M() is Mertens function²⁷⁶
• 1404 = heptagonal number⁶⁸
• 1405 = 26² + 27², 7² + 8² + ... + 16², centered square number¹⁴
• 1406 = pronic number,⁵¹ semi-meandric number²⁷⁷
• 1407 = 38² - 38 + 1 = H₃₈ (the 38th Hogben number)¹⁶⁵
• 1408 = maximal number of regions the plane is divided into by drawing 38 circles²⁰⁶
• 1409 = super-prime, Sophie Germain prime,¹³ smallest number whose eighth power is the sum of 8 eighth powers, Proth prime¹⁴⁰
• 1410 = denominator of the 46th Bernoulli number²⁷⁸
• 1411 = LS(41)²⁷⁹
• 1412 = LS(42),²⁷⁹ spy number
• 1413 = LS(43)²⁷⁹
• 1414 = smallest composite that when added to sum of prime factors reaches a prime after 27 iterations²⁸⁰
• 1415 = the Mahonian number: T(8, 8)¹⁸⁹
• 1416 = LS(46)²⁷⁹
• 1417 = number of partitions of 32 in which the number of parts divides 32²⁸¹
• 1418 = smallest x such that M(x) = 13, where M() is Mertens function²⁷⁶
• 1419 = Zeisel number²⁸²
• 1420 = Number of partitions of 56 into prime parts
• 1421 = maximum dimension of Euclidean spaces which suffice for every smooth compact Riemannian 29-manifold to be realizable as a sub-manifold,²⁸³ spy number
• 1422 = number of partitions of 15 with two parts marked²⁸⁴
• 1423 = 200 + 1223 and the 200th prime is 1223; 1423 is also prime²⁸⁵
• 1424 = number of nonnegative solutions to x² + y² ≤ 42²²⁵⁴
• 1425 = self-descriptive number in base 5
• 1426 = sum of totient function for first 68 integers, pentagonal number,⁷³ number of strict partions of 42¹⁰⁸
• 1427 = twin prime together with 1429²⁸⁶
• 1428 = number of complete ternary trees with 6 internal nodes, or 18 edges;²⁸⁷ the first 4 digits of the repeating decimal for 1/7 (0.142857)
• 1429 = number of partitions of 53 such that the smallest part is greater than or equal to number of parts²²⁵
• 1430 = Catalan number²⁸⁸
• 1431 = 53rd triangular number,²⁸ hexagonal number²⁹
• 1432 = member of Padovan sequence⁷⁵
• 1433 = super-prime, Honaker prime,²²⁶ typical port used for remote connections to Microsoft SQL Server databases
• 1434 = rounded volume of a regular tetrahedron with edge length 23²⁸⁹
• 1435 = vampire number;²⁰⁵ the standard railway gauge in millimetres, equivalent to 4 feet 8+1⁄2 inches (1.435 m)
• 1436 = discriminant of a totally real cubic field²⁹⁰
• 1437 = smallest number of complexity 20: smallest number requiring 20 1's to build using +, * and ^²⁹¹
• 1438 = k such that 5 × 2^k - 1 is prime²⁴³
• 1439 = Sophie Germain prime,¹³ safe prime²²
• 1440 = a highly totient number,¹³⁹ a largely composite number⁷⁴ and a 481-gonal number. Also, the number of minutes in one day, the size in kibibytes (units of 1,024 bytes) of a standard ⁠3+1/2⁠ floppy disk, and the horizontal resolution of WXGA(II) computer displays
• 1441 = star number⁸⁸
• 1442 = number of parts in all partitions of 31 into distinct parts⁴⁵
• 1443 = the sum of the second trio of three-digit permutable primes in decimal: 337, 373, and 733. Also the number of edges in the join of two cycle graphs, both of order 37¹⁴²
• 1444 = 38², smallest pandigital number in Roman numerals
• 1445 = ${\displaystyle \sum _{k=0}^{3}\left({\binom {3}{k}}\times {\binom {3+k}{k}}\right)^{2}}$²⁹²
• 1446 = number of points on surface of octahedron with edge length 19¹⁴⁶
• 1447 = super-prime, happy number
• 1448 = number k such that phi(prime(k)) is a square²⁹³
• 1449 = Stella octangula number
• 1450 = σ₂(34): sum of squares of divisors of 34²⁶¹
• 1451 = Sophie Germain prime¹³
• 1452 = first Zagreb index of the complete graph K₁₂²⁹⁴
• 1453 = Sexy prime with 1459
• 1454 = 3 × 22² + 2 = number of points on surface of square pyramid of side-length 22²⁹⁵
• 1455 = k such that geometric mean of phi(k) and sigma(k) is an integer²⁹⁶
• 1456 = number of regions in regular 15-gon with all diagonals drawn²⁹⁷
• 1457 = 2 × 27² − 1 = a twin square²⁹⁸
• 1458 = maximum determinant of an 11 by 11 matrix of zeroes and ones, 3-smooth number (2×3⁶)
• 1459 = Sexy prime with 1453, sum of nine consecutive primes (139 + 149 + 151 + 157 + 163 + 167 + 173 + 179 + 181), Pierpont prime
• 1460 = The number of years that would have to pass in the Julian calendar in order to accrue a full year's worth of leap days.
• 1461 = number of partitions of 38 into prime power parts²⁰⁹
• 1462 = (35 - 1) × (35 + 8) = the first Zagreb index of the wheel graph with 35 vertices²⁹⁹
• 1463 = total number of parts in all partitions of 16⁶⁵
• 1464 = rounded total surface area of a regular icosahedron with edge length 13³⁰⁰
• 1465 = 5-Knödel number¹³⁴
• 1466 = ${\displaystyle \sum _{k=1}^{256}d(k)}$, where ${\displaystyle d(k)}$ = number of divisors of ${\displaystyle k}$³⁰¹
• 1467 = number of partitions of 39 with zero crank³⁰²
• 1468 = number of polyhexes with 11 cells that tile the plane by translation³⁰³
• 1469 = octahedral number,¹⁴³ highly cototient number⁴³
• 1470 = pentagonal pyramidal number,³⁰⁴ sum of totient function for first 69 integers
• 1471 = super-prime, centered heptagonal number⁶⁹
• 1472 = number of overpartitions of 15³⁰⁵
• 1473 = cropped hexagone²⁴⁴
• 1474 = ${\displaystyle {\frac {44(44+1)}{2}}+{\frac {44^{2}}{4}}}$: triangular number plus quarter square (i.e., A000217(44) + A002620(44))³⁰⁶
• 1475 = number of partitions of 33 into parts each of which is used a different number of times³⁰⁷
• 1476 = coreful perfect number³⁰⁸
• 1477 = 7-Knödel number¹³⁰
• 1478 = total number of largest parts in all compositions of 11³⁰⁹
• 1479 = number of planar partitions of 12³¹⁰
• 1480 = sum of the first 29 primes
• 1481 = Sophie Germain prime¹³
• 1482 = pronic number,⁵¹ number of unimodal compositions of 15 where the maximal part appears once³¹¹
• 1483 = 39² - 39 + 1 = H₃₉ (the 39th Hogben number)¹⁶⁵
• 1484 = maximal number of regions the plane is divided into by drawing 39 circles²⁰⁶
• 1485 = 54th triangular number²⁸
• 1486 = number of strict solid partitions of 19⁹¹
• 1487 = safe prime²²
• 1488 = triangular matchstick number,⁴⁸ commonly used as a hate symbol
• 1489 = centered triangular number¹²⁵
• 1490 = tetranacci number³¹²
• 1491 = nonagonal number,¹⁸⁰ Mertens function zero
• 1492 = discriminant of a totally real cubic field,²⁹⁰ Mertens function zero
• 1493 = Stern prime¹⁶²
• 1494 = sum of totient function for first 70 integers
• 1495 = 9###³¹³
• 1496 = square pyramidal number¹⁷
• 1497 = skiponacci number¹²¹
• 1498 = number of flat partitions of 41³¹⁴
• 1499 = Sophie Germain prime,¹³ super-prime

• 1500 = hypotenuse in three different Pythagorean triangles³¹⁵
• 1501 = centered pentagonal number⁴⁶
• 1502 = number of pairs of consecutive integers x, x+1 such that all prime factors of both x and x+1 are at most 47³¹⁶
• 1503 = least number of triangles of the Spiral of Theodorus to complete 12 revolutions²¹⁰
• 1504 = primitive abundant number (abundant number all of whose proper divisors are deficient numbers)²⁶²
• 1505 = number of integer partitions of 41 with distinct differences between successive parts³¹⁷
• 1506 = number of Golomb partitions of 28³¹⁸
• 1507 = number of partitions of 32 that do not contain 1 as a part³⁴
• 1508 = heptagonal pyramidal number¹⁵¹
• 1509 = pinwheel number⁹⁵
• 1510 = deficient number, odious number
• 1511 = Sophie Germain prime,¹³ balanced prime⁹⁶
• 1512 = k such that geometric mean of phi(k) and sigma(k) is an integer²⁹⁶
• 1513 = centered square number¹⁴
• 1514 = sum of first 44 composite numbers¹⁷⁹
• 1515 = maximum dimension of Euclidean spaces which suffice for every smooth compact Riemannian 30-manifold to be realizable as a sub-manifold²⁸³
• 1516 = ${\displaystyle \left\lfloor 9^{\frac {10}{3}}\right\rfloor }$³¹⁹
• 1517 = number of lattice points inside a circle of radius 22¹²⁰
• 1518 = sum of first 32 semiprimes,³²⁰ Mertens function zero
• 1519 = number of polyhexes with 8 cells,³²¹ Mertens function zero
• 1520 = pentagonal number,⁷³ Mertens function zero, forms a Ruth–Aaron pair with 1521 under second definition
• 1521 = 39², Mertens function zero, centered octagonal number,¹⁸⁴ forms a Ruth–Aaron pair with 1520 under second definition
• 1522 = k such that 5 × 2^k - 1 is prime²⁴³
• 1523 = super-prime, Mertens function zero, safe prime,²² member of the Mian–Chowla sequence¹⁸
• 1524 = Mertens function zero, k such that geometric mean of phi(k) and sigma(k) is an integer²⁹⁶
• 1525 = heptagonal number,⁶⁸ Mertens function zero
• 1526 = number of conjugacy classes in the alternating group A₂₇³²²
• 1527 = number of 2-dimensional partitions of 11,³²³ Mertens function zero
• 1528 = Mertens function zero, rounded total surface area of a regular octahedron with edge length 21³²⁴
• 1529 = composite de Polignac number¹⁷⁵
• 1530 = vampire number²⁰⁵
• 1531 = prime number, centered decagonal number, Mertens function zero
• 1532 = number of series-parallel networks with 9 unlabeled edges,³²⁵ Mertens function zero
• 1533 = 21 × 73 = 21 × 21st prime²¹³
• 1534 = number of achiral integer partitions of 50²⁵⁶
• 1535 = Thabit number
• 1536 = a common size of microplate, 3-smooth number (2⁹×3), number of threshold functions of exactly 4 variables³²⁶
• 1537 = Keith number,⁹⁷ Mertens function zero
• 1538 = number of surface points on a cube with edge-length 17¹⁹
• 1539 = maximal number of pieces that can be obtained by cutting an annulus with 54 cuts¹¹⁷
• 1540 = 55th triangular number,²⁸ hexagonal number,²⁹ decagonal number,⁹⁹ tetrahedral number¹²⁹
• 1541 = octagonal number¹⁴⁸
• 1542 = k such that 2^k starts with k³²⁷
• 1543 = prime dividing all Fibonacci sequences,³²⁸ Mertens function zero
• 1544 = Mertens function zero, number of partitions of integer partitions of 17 where all parts have the same length³²⁹
• 1545 = number of reversible string structures with 9 beads using exactly three different colors³³⁰
• 1546 = number of 5 X 5 binary matrices with at most one 1 in each row and column,³³¹ Mertens function zero
• 1547 = hexagonal pyramidal number
• 1548 = coreful perfect number³⁰⁸
• 1549 = de Polignac prime³³²
• 1550 = ${\displaystyle {\frac {31\times (3\times 31+7)}{2}}}$ = number of cards needed to build a 31-tier house of cards with a flat, one-card-wide roof³³³
• 1551 = 6920 - 5369 = A169952(24) - A169952(23) = A169942(24) = number of Golomb rulers of length 24³³⁴³³⁵
• 1552 = Number of partitions of 57 into prime parts
• 1553 = 509 + 521 + 523 = a prime that is the sum of three consecutive primes³³⁶
• 1554 = 2 × 3 × 7 × 37 = product of four distinct primes³³⁷
• 1555² divides 6^1554338
• 1556 = sum of the squares of the first nine primes
• 1557 = number of graphs with 8 nodes and 13 edges³³⁹
• 1558 = number k such that k⁶⁴ + 1 is prime
• 1559 = Sophie Germain prime¹³
• 1560 = pronic number⁵¹
• 1561 = a centered octahedral number,¹⁴⁷ number of series-reduced trees with 19 nodes³⁴⁰
• 1562 = maximal number of regions the plane is divided into by drawing 40 circles²⁰⁶
• 1563 = ${\displaystyle \sum _{k=1}^{50}{\frac {50}{\gcd(50,k)}}}$³⁴¹
• 1564 = sum of totient function for first 71 integers
• 1565 = ${\displaystyle {\sqrt {1036^{2}+1173^{2}}}}$ and ${\displaystyle 1036+1173=47^{2}}$³⁴²
• 1566 = number k such that k⁶⁴ + 1 is prime
• 1567 = number of partitions of 24 with at least one distinct part²⁰⁰
• 1568 = Achilles number³⁴³
• 1569 = 2 × 28² + 1 = number of different 2 × 2 determinants with integer entries from 0 to 28¹⁹⁹
• 1570 = 2 × 28² + 2 = number of points on surface of tetrahedron with edgelength 28¹⁴¹
• 1571 = Honaker prime²²⁶
• 1572 = member of the Mian–Chowla sequence¹⁸
• 1573 = discriminant of a totally real cubic field²⁹⁰
• 1574²⁵⁶ + 1 is prime³⁴⁴
• 1575 = odd abundant number,³⁴⁵ sum of the nontriangular numbers between successive triangular numbers, number of partitions of 24²⁰²
• 1576¹⁴ == 1 (mod 15^2)³⁴⁶
• 1577 = sum of the quadratic residues of 83³⁴⁷
• 1578 = sum of first 45 composite numbers¹⁷⁹
• 1579 = number of partitions of 54 such that the smallest part is greater than or equal to number of parts²²⁵
• 1580 = number of achiral integer partitions of 51²⁵⁶
• 1581 = number of edges in the hexagonal triangle T(31)¹²²
• 1582 = a number such that the integer triangle [A070080(1582), A070081(1582), A070082(1582)] has an integer area³⁴⁸
• 1583 = Sophie Germain prime
• 1584 = triangular matchstick number⁴⁸
• 1585 = Riordan number, centered triangular number¹²⁵
• 1586 = area of the 23rd conjoined trapezoid¹⁶⁹
• 1587 = 3 × 23² = number of edges of a complete tripartite graph of order 69, K_23,23,23³⁴⁹
• 1588 = sum of totient function for first 72 integers
• 1589 = composite de Polignac number¹⁷⁵
• 1590 = rounded volume of a regular icosahedron with edge length 9³⁵⁰
• 1591 = rounded volume of a regular octahedron with edge length 15²²⁴
• 1592 = sum of all divisors of the first 36 odd numbers³⁵¹
• 1593 = sum of the first 30 primes
• 1594 = minimal cost of maximum height Huffman tree of size 17³⁵²
• 1595 = number of non-isomorphic set-systems of weight 10
• 1596 = 56th triangular number²⁸
• 1597 = Fibonacci prime,³⁵³ Markov prime,²³⁸ super-prime, emirp
• 1598 = number of unimodular 2 × 2 matrices having all terms in {0,1,...,25}¹¹²
• 1599 = number of edges in the join of two cycle graphs, both of order 39¹⁴²

• 1600 = 40², structured great rhombicosidodecahedral number,³⁵⁴ repdigit in base 7 (4444₇), street number on Pennsylvania Avenue of the White House, length in meters of a common High School Track Event, perfect score on SAT (except from 2005 to 2015)
• 1601 = Sophie Germain prime, Proth prime,¹⁴⁰ the novel 1601 (Mark Twain)
• 1602 = number of points on surface of octahedron with edgelength 20¹⁴⁶
• 1603 = number of partitions of 27 with nonnegative rank³⁵⁵
• 1604 = number of compositions of 22 into prime parts³⁵⁶
• 1605 = number of polyominoes consisting of 7 regular octagons³⁵⁷
• 1606 = enneagonal pyramidal number³⁵⁸
• 1607 = member of prime triple with 1609 and 1613³⁵⁹
• 1608 = ${\displaystyle \sum _{k=1}^{44}\sigma (k)}$¹⁶⁸
• 1609 = cropped hexagonal number²⁴⁴
• 1610 = number of strict partions of 43¹⁰⁸
• 1611 = number of rational numbers which can be constructed from the set of integers between 1 and 51¹⁵²
• 1612 = maximum dimension of Euclidean spaces which suffice for every smooth compact Riemannian 31-manifold to be realizable as a sub-manifold²⁸³
• 1613, 1607 and 1619 are all primes³⁶⁰
• 1614 = number of ways of refining the partition 8^1 to get 1^8³⁶¹
• 1615 = composite number such that the square mean of its prime factors is a nonprime integer³⁶²
• 1616 = ${\displaystyle {\frac {16(16^{2}+3\times 16-1)}{3}}}$ = number of monotonic triples (x,y,z) in {1,2,...,16}³³⁶³
• 1617 = pentagonal number⁷³
• 1618 = centered heptagonal number⁶⁹
• 1619 = palindromic prime in binary, safe prime²²
• 1620 = 809 + 811: sum of twin prime pair¹⁹²
• 1621 = super-prime, pinwheel number⁹⁵
• 1622 = semiprime of the form prime + 1³⁶⁴
• 1623 is not the sum of two triangular numbers and a fourth power³⁶⁵
• 1624 = number of squares in the Aztec diamond of order 28³⁶⁶
• 1625 = centered square number¹⁴
• 1626 = centered pentagonal number⁴⁶
• 1627 = prime and 2 × 1627 - 1 = 3253 is also prime³⁶⁷
• 1628 = centered pentagonal number⁴⁶
• 1629 = rounded volume of a regular tetrahedron with edge length 24²⁸⁹
• 1630 = number k such that k^64 + 1 is prime
• 1631 = ${\displaystyle \sum _{k=0}^{5}(k+1)!{\binom {5}{k}}}$³⁶⁸
• 1632 = number of acute triangles made from the vertices of a regular 18-polygon³⁶⁹
• 1633 = star number⁸⁸
• 1634 = the smallest four-digit Narcissistic number in base 10
• 1635 = number of partitions of 56 whose reciprocal sum is an integer³⁷⁰
• 1636 = number of nonnegative solutions to x² + y² ≤ 45²²⁵⁴
• 1637 = prime island: least prime whose adjacent primes are exactly 30 apart³⁷¹
• 1638 = harmonic divisor number,³⁷² 5 × 2¹⁶³⁸ - 1 is prime²⁴³
• 1639 = nonagonal number¹⁸⁰
• 1640 = pronic number⁵¹
• 1641 = 41² - 41 + 1 = H₄₁ (the 41st Hogben number)¹⁶⁵
• 1642 = maximal number of regions the plane is divided into by drawing 41 circles²⁰⁶
• 1643 = sum of first 46 composite numbers¹⁷⁹
• 1644 = 821 + 823: sum of twin prime pair¹⁹²
• 1645 = number of 16-celled pseudo still lifes in Conway's Game of Life, up to rotation and reflection³⁷³
• 1646 = number of graphs with 8 nodes and 14 edges³³⁹
• 1647 and 1648 are both divisible by cubes³⁷⁴
• 1648 = number of partitions of 34³ into distinct cubes³⁷⁵
• 1649 = highly cototient number,⁴³ Leyland number¹¹⁵ using 4 & 5 (4⁵ + 5⁴)
• 1650 = number of cards to build an 33-tier house of cards¹⁶⁴
• 1651 = heptagonal number⁶⁸
• 1652 = number of partitions of 29 into a prime number of parts¹¹⁰
• 1653 = 57th triangular number,²⁸ hexagonal number,²⁹ number of lattice points inside a circle of radius 23¹²⁰
• 1654 = number of partitions of 42 into divisors of 42³⁷⁶
• 1655 = rounded volume of a regular dodecahedron with edge length 6³⁷⁷
• 1656 = 827 + 829: sum of twin prime pair¹⁹²
• 1657 = cuban prime,³⁷⁸ prime of the form 2p-1
• 1658 = smallest composite that when added to sum of prime factors reaches a prime after 25 iterations²⁸⁰
• 1659 = number of rational numbers which can be constructed from the set of integers between 1 and 52¹⁵²
• 1660 = sum of totient function for first 73 integers
• 1661 = 11 × 151, palindrome that is a product of two palindromic primes¹⁰⁵
• 1662 = number of partitions of 49 into pairwise relatively prime parts¹⁶¹
• 1663 = a prime number and 5¹⁶⁶³ - 4¹⁶⁶³ is a 1163-digit prime number³⁷⁹
• 1664 = k such that k, k+1 and k+2 are sums of 2 squares³⁸⁰
• 1665 = centered tetrahedral number²³⁹
• 1666 = largest efficient pandigital number in Roman numerals (each symbol occurs exactly once)
• 1667 = 228 + 1439 and the 228th prime is 1439²⁸⁵
• 1668 = number of partitions of 33 into parts all relatively prime to 33³⁸¹
• 1669 = super-prime, smallest prime with a gap of exactly 24 to the next prime³⁸²
• 1670 = number of compositions of 12 such that at least two adjacent parts are equal³⁸³
• 1671 divides the sum of the first 1671 composite numbers³⁸⁴
• 1672 = 41² - 3², the only way to express 1672 as a difference of prime squares²⁴⁵
• 1673 = RMS number³⁸⁵
• 1674 = k such that geometric mean of phi(k) and sigma(k) is an integer²⁹⁶
• 1675 = Kin number³⁸⁶
• 1676 = number of partitions of 34 into parts each of which is used a different number of times³⁰⁷
• 1677 = 41² - 2², the only way to express 1677 as a difference of prime squares²⁴⁵
• 1678 = n such that n³² + 1 is prime¹³¹
• 1679 = highly cototient number,⁴³ semiprime (23 × 73, see also Arecibo message), number of parts in all partitions of 32 into distinct parts⁴⁵
• 1680 = the 17th highly composite number,²⁰⁴ number of edges in the join of two cycle graphs, both of order 40¹⁴²
• 1681 = 41², smallest number yielded by the formula n² + n + 41 that is not a prime; centered octagonal number¹⁸⁴
• 1682 = and 1683 is a member of a Ruth–Aaron pair (first definition)
• 1683 = triangular matchstick number⁴⁸
• 1684 = centered triangular number¹²⁵
• 1685 = 5-Knödel number¹³⁴
• 1686 = ${\displaystyle \sum _{k=1}^{45}\sigma (k)}$¹⁶⁸
• 1687 = 7-Knödel number¹³⁰
• 1688 = number of finite connected sets of positive integers greater than one with least common multiple 72³⁸⁷
• 1689 = ${\displaystyle 9!!\sum _{k=0}^{4}{\frac {1}{2k+1}}}$³⁸⁸
• 1690 = number of compositions of 14 into powers of 2³⁸⁹
• 1691 = the same upside down, which makes it a strobogrammatic number³⁹⁰
• 1692 = coreful perfect number³⁰⁸
• 1693 = smallest prime > 41².¹⁴⁹
• 1694 = number of unimodular 2 × 2 matrices having all terms in {0,1,...,26}¹¹²
• 1695 = magic constant of n × n normal magic square and n-queens problem for n = 15. Number of partitions of 58 into prime parts
• 1696 = sum of totient function for first 74 integers
• 1697 = Friedlander-Iwaniec prime¹⁰³
• 1698 = number of rooted trees with 47 vertices in which vertices at the same level have the same degree²⁰⁸
• 1699 = number of rooted trees with 48 vertices in which vertices at the same level have the same degree²⁰⁸

• 1700 = σ₂(39): sum of squares of divisors of 39²⁶¹
• 1701 = ${\displaystyle \left\{{8 \atop 4}\right\}}$, decagonal number, hull number of the U.S.S. Enterprise on Star Trek
• 1702 = palindromic in 3 consecutive bases: 898₁₄, 787₁₅, 6A6₁₆
• 1703 = 1703131131 / 1000077 and the divisors of 1703 are 1703, 131, 13 and 1³⁹¹
• 1704 = sum of the squares of the parts in the partitions of 18 into two distinct parts³⁹²
• 1705 = tribonacci number³⁹³
• 1706 = 1 + 4 + 16 + 64 + 256 + 1024 + 256 + 64 + 16 + 4 + 1 sum of fifth row of triangle of powers of 4³⁹⁴
• 1707 = number of partitions of 30 in which the number of parts divides 30²⁸¹
• 1708 = 2² × 7 × 61 a number whose product of prime indices 1 × 1 × 4 × 18 is divisible by its sum of prime factors 2 + 2 + 7 + 61³⁹⁵
• 1709 = first of a sequence of eight primes formed by adding 57 in the middle. 1709, 175709, 17575709, 1757575709, 175757575709, 17575757575709, 1757575757575709 and 175757575757575709 are all prime, but 17575757575757575709 = 232433 × 75616446785773
• 1710 = maximal number of pieces that can be obtained by cutting an annulus with 57 cuts¹¹⁷
• 1711 = 58th triangular number,²⁸ centered decagonal number
• 1712 = number of irredundant sets in the 29-cocktail party graph²¹⁴
• 1713 = number of aperiodic rooted trees with 12 nodes³⁹⁶
• 1714 = number of regions formed by drawing the line segments connecting any two of the 18 perimeter points of an 3 × 6 grid of squares³⁹⁷
• 1715 = k such that geometric mean of phi(k) and sigma(k) is an integer²⁹⁶
• 1716 = 857 + 859: sum of twin prime pair,¹⁹² a binomial coefficient, equal to ${\displaystyle {\tbinom {13}{6}}}$.
• 1717 = pentagonal number⁷³
• 1718 = ${\displaystyle \sum _{d|12}{\binom {12}{d}}}$³⁹⁸
• 1719 = composite de Polignac number¹⁷⁵
• 1720 = sum of the first 31 primes
• 1721 = twin prime; number of squares between 42² and 42⁴.¹¹⁴
• 1722 = Giuga number,³⁹⁹ pronic number⁵¹
• 1723 = super-prime
• 1724 = maximal number of regions the plane is divided into by drawing 42 circles²⁰⁶
• 1725 = 47² - 22² = (prime(15))² - (nonprime(15))²⁴⁰⁰
• 1726 = number of partitions of 44 into distinct and relatively prime parts⁴⁰¹
• 1727 = area of the 24th conjoined trapezoid¹⁶⁹
• 1728 = the quantity expressed as 1000 in duodecimal, that is, the cube of twelve (called a great gross), and so, the number of cubic inches in a cubic foot, palindromic in base 11 (1331₁₁) and 23 (363₂₃)
• 1729 = taxicab number, Carmichael number, Zeisel number, centered cube number, Hardy–Ramanujan number. In the decimal expansion of e the first time all 10 digits appear in sequence starts at the 1729th digit (or 1728th decimal place). In 1979 the rock musical Hair closed on Broadway in New York City after 1729 performances. Palindromic in bases 12, 32, 36.
• 1730 = 3 × 24² + 2 = number of points on surface of square pyramid of side-length 24²⁹⁵
• 1731 = k such that geometric mean of phi(k) and sigma(k) is an integer²⁹⁶
• 1732 = ${\displaystyle \sum _{k=0}^{5}{\binom {5}{k}}^{k}}$⁴⁰²
• 1733 = Sophie Germain prime, palindromic in bases 3, 18, 19.
• 1734 = surface area of a cube of edge length 17⁴⁰³
• 1735 = number of partitions of 55 such that the smallest part is greater than or equal to number of parts²²⁵
• 1736 = sum of totient function for first 75 integers, number of surface points on a cube with edge-length 18¹⁹
• 1737 = pinwheel number⁹⁵
• 1738 = number of achiral integer partitions of 52²⁵⁶
• 1739 = number of 1s in all partitions of 30 into odd parts⁴⁰⁴
• 1740 = number of squares in the Aztec diamond of order 29³⁶⁶
• 1741 = super-prime, centered square number¹⁴
• 1742 = number of regions the plane is divided into by 30 ellipses¹⁰¹
• 1743 = wiener index of the windmill graph D(3,21)¹²⁸
• 1744 = k such that k, k+1 and k+2 are sums of 2 squares³⁸⁰
• 1745 = 5-Knödel number¹³⁴
• 1746 = number of unit-distance graphs on 8 nodes⁴⁰⁵
• 1747 = balanced prime⁹⁶
• 1748 = number of partitions of 55 into distinct parts in which the number of parts divides 55⁴⁰⁶
• 1749 = number of integer partitions of 33 with no part dividing all the others²³⁰
• 1750 = hypotenuse in three different Pythagorean triangles³¹⁵
• 1751 = cropped hexagone²⁴⁴
• 1752 = 79² - 67², the only way to express 1752 as a difference of prime squares²⁴⁵
• 1753 = balanced prime⁹⁶
• 1754 = k such that 5*2^k - 1 is prime²⁴³
• 1755 = number of integer partitions of 50 whose augmented differences are distinct²⁷⁴
• 1756 = centered pentagonal number⁴⁶
• 1757 = least number of triangles of the Spiral of Theodorus to complete 13 revolutions²¹⁰
• 1758 = ${\displaystyle \sum _{k=1}^{46}\sigma (k)}$¹⁶⁸
• 1759 = de Polignac prime³³²
• 1760 = the number of yards in a mile
• 1761 = k such that k, k+1 and k+2 are products of two primes²⁴⁶
• 1762 = number of binary sequences of length 12 and curling number 2⁴⁰⁷
• 1763 = number of edges in the join of two cycle graphs, both of order 41¹⁴²
• 1764 = 42²
• 1765 = number of stacks, or planar partitions of 15⁴⁰⁸
• 1766 = number of points on surface of octahedron with edge length 21¹⁴⁶
• 1767 = σ(28²) = σ(35²)⁴⁰⁹
• 1768 = number of nonequivalent dissections of an hendecagon into 8 polygons by nonintersecting diagonals up to rotation⁴¹⁰
• 1769 = maximal number of pieces that can be obtained by cutting an annulus with 58 cuts¹¹⁷
• 1770 = 59th triangular number,²⁸ hexagonal number,²⁹ Seventeen Seventy, town in Australia
• 1771 = tetrahedral number¹²⁹
• 1772 = centered heptagonal number,⁶⁹ sum of totient function for first 76 integers
• 1773 = number of words of length 5 over the alphabet {1,2,3,4,5} such that no two even numbers appear consecutively⁴¹¹
• 1774 = number of rooted identity trees with 15 nodes and 5 leaves⁴¹²
• 1775 = ${\displaystyle \sum _{1\leq i\leq 10}prime(i)\cdot (2\cdot i-1)}$: sum of piles of first 10 primes⁴¹³
• 1776 = 24th square star number.⁴¹⁴ The number of pieces that could be seen in a 7 × 7 × 7× 7 Rubik's Tesseract.
• 1777 = smallest prime > 42².¹⁴⁹
• 1778 = least k >= 1 such that the remainder when 6^k is divided by k is 22⁴¹⁵
• 1779 = number of achiral integer partitions of 53²⁵⁶
• 1780 = number of lattice paths from (0, 0) to (7, 7) using E (1, 0) and N (0, 1) as steps that horizontally cross the diagonal y = x with even many times⁴¹⁶
• 1781 = the first 1781 digits of e form a prime⁴¹⁷
• 1782 = heptagonal number⁶⁸
• 1783 = de Polignac prime³³²
• 1784 = number of subsets of {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12} such that every pair of distinct elements has a different quotient⁴¹⁸
• 1785 = square pyramidal number,¹⁷ triangular matchstick number⁴⁸
• 1786 = centered triangular number¹²⁵
• 1787 = super-prime, sum of eleven consecutive primes (137 + 139 + 149 + 151 + 157 + 163 + 167 + 173 + 179 + 181 + 191)
• 1788 = Euler transform of -1, -2, ..., -34⁴¹⁹
• 1789 = number of wiggly sums adding to 17 (terms alternately increase and decrease or vice versa)⁴²⁰
• 1790 = number of partitions of 50 into pairwise relatively prime parts¹⁶¹
• 1791 = largest natural number that cannot be expressed as a sum of at most four hexagonal numbers.
• 1792 = Granville number
• 1793 = number of lattice points inside a circle of radius 24¹²⁰
• 1794 = nonagonal number,¹⁸⁰ number of partitions of 33 that do not contain 1 as a part³⁴
• 1795 = number of heptagons with perimeter 38⁴²¹
• 1796 = k such that geometric mean of phi(k) and sigma(k) is an integer²⁹⁶
• 1797 = number k such that phi(prime(k)) is a square²⁹³
• 1798 = 2 × 29 × 31 = 10₂ × 11101₂ × 11111₂, which yield zero when the prime factors are xored together⁴²²
• 1799 = 2 × 30² − 1 = a twin square²⁹⁸

• 1800 = pentagonal pyramidal number,³⁰⁴ Achilles number, also, in da Ponte's Don Giovanni, the number of women Don Giovanni had slept with so far when confronted by Donna Elvira, according to Leporello's tally
• 1801 = cuban prime, sum of five and nine consecutive primes (349 + 353 + 359 + 367 + 373 and 179 + 181 + 191 + 193 + 197 + 199 + 211 + 223 + 227)³⁷⁸
• 1802 = 2 × 30² + 2 = number of points on surface of tetrahedron with edge length 30,¹⁴¹ number of partitions of 30 such that the number of odd parts is a part¹⁷³
• 1803 = number of decahexes that tile the plane isohedrally but not by translation or by 180-degree rotation (Conway criterion)⁴²³
• 1804 = number k such that k^64 + 1 is prime
• 1805 = number of squares between 43² and 43⁴.¹¹⁴
• 1806 = pronic number,⁵¹ product of first four terms of Sylvester's sequence, primary pseudoperfect number,⁴²⁴ only number for which n equals the denominator of the nth Bernoulli number,⁴²⁵ Schröder number⁴²⁶
• 1807 = fifth term of Sylvester's sequence⁴²⁷
• 1808 = maximal number of regions the plane is divided into by drawing 43 circles²⁰⁶
• 1809 = sum of first 17 super-primes⁴²⁸
• 1810 = ${\displaystyle \sum _{k=0}^{4}{\binom {4}{k}}^{4}}$⁴²⁹
• 1811 = Sophie Germain prime
• 1812 = n such that n³² + 1 is prime¹³¹
• 1813 = number of polyominoes with 26 cells, symmetric about two orthogonal axes⁴³⁰
• 1814 = 1 + 6 + 36 + 216 + 1296 + 216 + 36 + 6 + 1 = sum of 4th row of triangle of powers of six⁴³¹
• 1815 = polygonal chain number ${\displaystyle \#(P_{2,1}^{3})}$⁴³²
• 1816 = number of strict partions of 44¹⁰⁸
• 1817 = total number of prime parts in all partitions of 20⁴³³
• 1818 = n such that n³² + 1 is prime¹³¹
• 1819 = sum of the first 32 primes, minus 32⁴³⁴
• 1820 = pentagonal number,⁷³ pentatope number,²⁵⁹ number of compositions of 13 whose run-lengths are either weakly increasing or weakly decreasing⁴³⁵
• 1821 = member of the Mian–Chowla sequence¹⁸
• 1822 = number of integer partitions of 43 whose distinct parts are connected²³²
• 1823 = super-prime, safe prime²²
• 1824 = 43² - 5², the only way to express 1824 as a difference of prime squares²⁴⁵
• 1825 = octagonal number¹⁴⁸
• 1826 = decagonal pyramidal number⁴
• 1827 = vampire number²⁰⁵
• 1828 = meandric number, open meandric number, appears twice in the first 10 decimal digits of e
• 1829 = composite de Polignac number¹⁷⁵
• 1830 = 60th triangular number²⁸
• 1831 = smallest prime with a gap of exactly 16 to next prime (1847)⁴³⁶
• 1832 = sum of totient function for first 77 integers
• 1833 = number of atoms in a decahedron with 13 shells⁴³⁷
• 1834 = octahedral number,¹⁴³ sum of the cubes of the first five primes
• 1835 = absolute value of numerator of ${\displaystyle D_{6}^{(5)}}$⁴³⁸
• 1836 = factor by which a proton is more massive than an electron
• 1837 = star number⁸⁸
• 1838 = number of unimodular 2 × 2 matrices having all terms in {0,1,...,27}¹¹²
• 1839 = ${\displaystyle \lfloor {\sqrt[{3}]{13!}}\rfloor }$⁴³⁹
• 1840 = 43² - 3², the only way to express 1840 as a difference of prime squares²⁴⁵
• 1841 = solution to the postage stamp problem with 3 denominations and 29 stamps,⁴⁴⁰ Mertens function zero
• 1842 = number of unlabeled rooted trees with 11 nodes⁴⁴¹
• 1843 = k such that phi(k) is a perfect cube,⁴⁴² Mertens function zero
• 1844 = 3⁷ - 7³,⁴⁴³ Mertens function zero
• 1845 = number of partitions of 25 containing at least one prime,⁴⁴⁴ Mertens function zero
• 1846 = sum of first 49 composite numbers¹⁷⁹
• 1847 = super-prime
• 1848 = number of edges in the join of two cycle graphs, both of order 42¹⁴²
• 1849 = 43², palindromic in base 6 (= 12321₆), centered octagonal number¹⁸⁴
• 1850 = Number of partitions of 59 into prime parts
• 1851 = sum of the first 32 primes
• 1852 = number of quantales on 5 elements, up to isomorphism⁴⁴⁵
• 1853 = sum of primitive roots of 27-th prime,⁴⁴⁶ Mertens function zero
• 1854 = number of permutations of 7 elements with no fixed points,⁴⁴⁷ Mertens function zero
• 1855 = rencontres number: number of permutations of [7] with exactly one fixed point⁴⁴⁸
• 1856 = sum of totient function for first 78 integers
• 1857 = Mertens function zero, pinwheel number⁹⁵
• 1858 = number of 14-carbon alkanes C₁₄H₃₀ ignoring stereoisomers⁴⁴⁹
• 1859 = composite de Polignac number¹⁷⁵
• 1860 = number of squares in the Aztec diamond of order 30⁴⁵⁰
• 1861 = centered square number,¹⁴ Mertens function zero
• 1862 = Mertens function zero, forms a Ruth–Aaron pair with 1863 under second definition
• 1863 = Mertens function zero, forms a Ruth–Aaron pair with 1862 under second definition
• 1864 = Mertens function zero, ${\displaystyle {\frac {1864!-2}{2}}}$ is a prime⁴⁵¹
• 1865 = 12345₆: Largest senary metadrome (number with digits in strict ascending order in base 6)⁴⁵²
• 1866 = Mertens function zero, number of plane partitions of 16 with at most two rows⁴⁵³
• 1867 = prime de Polignac number³³²
• 1868 = smallest number of complexity 21: smallest number requiring 21 1's to build using +, * and ^²⁹¹
• 1869 = Hultman number: S_H(7, 4)⁴⁵⁴
• 1870 = decagonal number⁹⁹
• 1871 = the first prime of the 2 consecutive twin prime pairs: (1871, 1873) and (1877, 1879)⁴⁵⁵
• 1872 = first Zagreb index of the complete graph K₁₃²⁹⁴
• 1873 = number of Narayana's cows and calves after 21 years²¹⁵
• 1874 = area of the 25th conjoined trapezoid¹⁶⁹
• 1875 = 50² - 25²
• 1876 = number k such that k^64 + 1 is prime
• 1877 = number of partitions of 39 where 39 divides the product of the parts⁴⁵⁶
• 1878 = n such that n³² + 1 is prime¹³¹
• 1879 = a prime with square index⁴⁵⁷
• 1880 = the 10th element of the self convolution of Lucas numbers⁴⁵⁸
• 1881 = tricapped prism number⁴⁵⁹
• 1882 = number of linearly separable Boolean functions in 4 variables⁴⁶⁰
• 1883 = number of conjugacy classes in the alternating group A₂₈³²²
• 1884 = k such that 5*2^k - 1 is prime²⁴³
• 1885 = Zeisel number²⁸²
• 1886 = number of partitions of 6⁴ into fourth powers⁴⁶¹
• 1887 = number of edges in the hexagonal triangle T(34)¹²²
• 1888 = primitive abundant number (abundant number all of whose proper divisors are deficient numbers)²⁶²
• 1889 = Sophie Germain prime, highly cototient number⁴³
• 1890 = triangular matchstick number⁴⁸
• 1891 = 61st triangular number,²⁸ sum of 5 consecutive primes (367 + 373 + 379 + 383 + 389) hexagonal number,²⁹ centered pentagonal number,⁴⁶ centered triangular number¹²⁵
• 1892 = pronic number⁵¹
• 1893 = 44² - 44 + 1 = H₄₄ (the 44th Hogben number)¹⁶⁵
• 1894 = maximal number of regions the plane is divided into by drawing 44 circles²⁰⁶
• 1895 = Stern-Jacobsthal number²⁵⁰
• 1896 = member of the Mian-Chowla sequence¹⁸
• 1897 = member of Padovan sequence,⁷⁵ number of triangle-free graphs on 9 vertices⁴⁶²
• 1898 = smallest multiple of n whose digits sum to 26⁴⁶³
• 1899 = cropped hexagone²⁴⁴

• 1900 = number of primes <= 2¹⁴²⁵
• 1901 = Sophie Germain prime, centered decagonal number
• 1902 = number of symmetric plane partitions of 27⁴⁶⁴
• 1903 = generalized Catalan number⁴⁶⁵
• 1904 = number of flat partitions of 43³¹⁴
• 1905 = Fermat pseudoprime¹⁰⁰
• 1906 = number n such that 3ⁿ - 8 is prime⁴⁶⁶
• 1907 = safe prime,²² balanced prime⁹⁶
• 1908 = coreful perfect number³⁰⁸
• 1909 = hyperperfect number⁴⁶⁷
• 1910 = number of compositions of 13 having exactly one fixed point⁴⁶⁸
• 1911 = heptagonal pyramidal number¹⁵¹
• 1912 = size of 6th maximum raising after one blind in pot-limit poker⁴⁶⁹
• 1913 = super-prime, Honaker prime²²⁶
• 1914 = number of bipartite partitions of 12 white objects and 3 black ones⁴⁷⁰
• 1915 = number of nonisomorphic semigroups of order 5⁴⁷¹
• 1916 = sum of first 50 composite numbers¹⁷⁹
• 1917 = number of partitions of 51 into pairwise relatively prime parts¹⁶¹
• 1918 = heptagonal number⁶⁸
• 1919 = smallest number with reciprocal of period length 36 in base 10⁴⁷²
• 1920 = sum of the nontriangular numbers between successive triangular numbers 120 and 136,
• 1921 = 4-dimensional centered cube number⁴⁷³
• 1922 = Area of a square with diagonal 62⁵⁴
• 1923 = 2 × 31² + 1 = number of different 2 X 2 determinants with integer entries from 0 to 31¹⁹⁹
• 1924 = 2 × 31² + 2 = number of points on surface of tetrahedron with edge length 31,¹⁴¹ sum of the first 36 semiprimes⁴⁷⁴
• 1925 = number of ways to write 24 as an orderless product of orderless sums¹⁰⁹
• 1926 = pentagonal number⁷³
• 1927 = 2¹¹ - 11²⁴⁷⁵
• 1928 = number of distinct values taken by 2^2^...^2 (with 13 2's and parentheses inserted in all possible ways)⁴⁷⁶
• 1929 = Mertens function zero, number of integer partitions of 42 whose distinct parts are connected²³²
• 1930 = number of pairs of consecutive integers x, x+1 such that all prime factors of both x and x+1 are at most 53³¹⁶
• 1931 = Sophie Germain prime
• 1932 = number of partitions of 40 into prime power parts²⁰⁹
• 1933 = centered heptagonal number,⁶⁹ Honaker prime²²⁶
• 1934 = sum of totient function for first 79 integers
• 1935 = number of edges in the join of two cycle graphs, both of order 43¹⁴²
• 1936 = 44², 18-gonal number,⁴⁷⁷ 324-gonal number.
• 1937 = number of chiral n-ominoes in 12-space, one cell labeled⁴⁷⁸
• 1938 = Mertens function zero, number of points on surface of octahedron with edge length 22¹⁴⁶
• 1939 = 7-Knödel number¹³⁰
• 1940 = the Mahonian number: T(8, 9)¹⁸⁹
• 1941 = maximal number of regions obtained by joining 16 points around a circle by straight lines⁴⁷⁹
• 1942 = number k for which 10k + 1, 10k + 3, 10k + 7, 10k + 9 and 10k + 13 are primes⁴⁸⁰
• 1943 = largest number not the sum of distinct tetradecagonal numbers⁴⁸¹
• 1944 = 3-smooth number (2³×3⁵), Achilles number³⁴³
• 1945 = number of partitions of 25 into relatively prime parts such that multiplicities of parts are also relatively prime⁴⁸²
• 1946 = number of surface points on a cube with edge-length 19¹⁹
• 1947 = k such that 5·2^k + 1 is a prime factor of a Fermat number 2^2m + 1 for some m⁴⁸³
• 1948 = number of strict solid partitions of 20⁹¹
• 1949 = smallest prime > 44².¹⁴⁹
• 1950 = ${\displaystyle 1\cdot 2\cdot 3+4\cdot 5\cdot 6+7\cdot 8\cdot 9+10\cdot 11\cdot 12}$,⁴⁸⁴ largest number not the sum of distinct pentadecagonal numbers⁴⁸¹
• 1951 = cuban prime³⁷⁸
• 1952 = number of covers of {1, 2, 3, 4}⁴⁸⁵
• 1953 = hexagonal prism number,⁴⁸⁶ 62nd triangular number²⁸
• 1954 = number of sum-free subsets of {1, ..., 16}²⁷³
• 1955 = number of partitions of 25 with at least one distinct part²⁰⁰
• 1956 = nonagonal number¹⁸⁰
• 1957 = ${\displaystyle \sum _{k=0}^{6}{\frac {6!}{k!}}}$ = total number of ordered k-tuples (k=0,1,2,3,4,5,6) of distinct elements from an 6-element set⁴⁸⁷
• 1958 = number of partitions of 25²⁰²
• 1959 = Heptanacci-Lucas number⁴⁸⁸
• 1960 = number of parts in all partitions of 33 into distinct parts⁴⁵
• 1961 = number of lattice points inside a circle of radius 25¹²⁰
• 1962 = number of edges in the join of the complete graph K₃₆ and the cycle graph C₃₆⁴⁸⁹
• 1963! - 1 is prime⁴⁹⁰
• 1964 = number of linear forests of planted planar trees with 8 nodes⁴⁹¹
• 1965 = total number of parts in all partitions of 17⁶⁵
• 1966 = sum of totient function for first 80 integers
• 1967 = least edge-length of a square dissectable into at least 30 squares in the Mrs. Perkins's quilt problem⁴⁹²
• σ(1968) = σ(1967) + σ(1966)⁴⁹³
• 1969 = Only value less than four million for which a "mod-ification" of the standard Ackermann Function does not stabilize⁴⁹⁴
• 1970 = number of compositions of two types of 9 having no even parts⁴⁹⁵
• 1971 = ${\displaystyle 3^{7}-6^{3}}$⁴⁹⁶
• 1972 = n such that ${\displaystyle {\frac {n^{37}-1}{n-1}}}$ is prime⁴⁹⁷
• 1973 = Sophie Germain prime, Leonardo prime
• 1974 = number of binary vectors of length 17 containing no singletons¹⁸¹
• 1975 = number of partitions of 28 with nonnegative rank³⁵⁵
• 1976 = octagonal number¹⁴⁸
• 1977 = number of non-isomorphic multiset partitions of weight 9 with no singletons⁴⁹⁸
• 1978 = n such that n | (3ⁿ + 5)⁴⁹⁹
• 1979 = number of squares between 45² and 45⁴,¹¹⁴ smallest number that is the sum of 4 positive cubes in at least 4 ways⁵⁰⁰
• 1980 = pronic number,⁵¹ highly abundant number with a greater sum of proper divisors than all smaller numbers⁵⁰¹
• 1981 = pinwheel number,⁹⁵ central polygonal number³⁰
• 1982 = maximal number of regions the plane is divided into by drawing 45 circles,²⁰⁶ a number with the property that 3¹⁹⁸² - 1982 is prime⁵⁰²
• 1983 = skiponacci number¹²¹
• 1984 = 11111000000 in binary, nonunitary perfect number,⁵⁰³ see also: 1984 (disambiguation)
• 1985 = centered square number¹⁴
• 1986 = number of ways to write 25 as an orderless product of orderless sums¹⁰⁹
• 1987 = 300th prime number
• 1988 = sum of the first 33 primes,⁵⁰⁴ sum of the first 51 composite numbers⁵⁰⁵
• 1989 = number of balanced primes less than 100,000,⁵⁰⁶ number of 9-step mappings with 4 inputs²⁶³
• 1990 = Stella octangula number
• 1991 = 11 × 181, the 46th Gullwing number,⁵⁰⁷ palindromic composite number with only palindromic prime factors⁵⁰⁸
• 1992 = number of nonisomorphic sets of nonempty subsets of a 4-set⁵⁰⁹
• 1993 = a number with the property that 4¹⁹⁹³ - 3¹⁹⁹³ is prime,⁵¹⁰ number of partitions of 30 into a prime number of parts¹¹⁰
• 1994 = Glaisher's function W(37)⁵¹¹
• 1995 = number of unlabeled graphs on 9 vertices with independence number 6⁵¹²
• 1996 = a number with the property that (1996! + 3)/3 is prime⁵¹³
• 1997 = ${\displaystyle \sum _{k=1}^{21}{k\cdot \phi (k)}}$⁵¹⁴
• 1998 = triangular matchstick number⁴⁸
• 1999 = centered triangular number,⁵¹⁵ number of regular forms in a myriagram.

There are 135 prime numbers between 1000 and 2000:⁵¹⁶⁵¹⁷

1009, 1013, 1019, 1021, 1031, 1033, 1039, 1049, 1051, 1061, 1063, 1069, 1087, 1091, 1093, 1097, 1103, 1109, 1117, 1123, 1129, 1151, 1153, 1163, 1171, 1181, 1187, 1193, 1201, 1213, 1217, 1223, 1229, 1231, 1237, 1249, 1259, 1277, 1279, 1283, 1289, 1291, 1297, 1301, 1303, 1307, 1319, 1321, 1327, 1361, 1367, 1373, 1381, 1399, 1409, 1423, 1427, 1429, 1433, 1439, 1447, 1451, 1453, 1459, 1471, 1481, 1483, 1487, 1489, 1493, 1499, 1511, 1523, 1531, 1543, 1549, 1553, 1559, 1567, 1571, 1579, 1583, 1597, 1601, 1607, 1609, 1613, 1619, 1621, 1627, 1637, 1657, 1663, 1667, 1669, 1693, 1697, 1699, 1709, 1721, 1723, 1733, 1741, 1747, 1753, 1759, 1777, 1783, 1787, 1789, 1801, 1811, 1823, 1831, 1847, 1861, 1867, 1871, 1873, 1877, 1879, 1889, 1901, 1907, 1913, 1931, 1933, 1949, 1951, 1973, 1979, 1987, 1993, 1997, 1999