262 = 2 x 131. It is the product of two distinct Sophie Germain primes . 262 is a meandric number : the number of ways a river can cross a ...

55 = 5 x 11. 55 is the tenth Fibonacci number . 55 is the tenth triangular number . 55 is a pyramidal number , the sum of the first five sq...

140 = 2 2 x 5 x 7. 140 has a unique representation as a sum of three squares: 140 = 2 2 + 6 2 + 10 2 . 140 is a square pyramidal number ....

434 = 2 x 7 x 31. 434 is a palindrome that produces a composed prime: 4 2 + 3 7 + 4 31 = 4611686018427390107, a prime. 434 is the smalles...

859 is a prime number. 857 and 859 form a twin prime pair. 859 is the largest prime that cannot be the central number in a 3-by-3 magic squa...

217 = 7 x 31. 217 is the ninth centered hexagonal (hex) number . 47 and 89 are primes, as is their concatenation: 4789. Inserting 0 betwee...

64 = 2 6 . 64 is the first number after 1 to be both a square and a cube: 64 = 8 2 = 4 3 . 64 is the number of integer partitions of 20 int...

522 = 2 x 3 2 x 29. 522 has a representation as a sum of two squares: 522 = 9 2 + 21 2 . 522 is the sum of six consecutive primes: 522 =...

703 = 19 x 37. 703 is the 37th triangular number . It is also a hexagonal number . 703 is a number that cannot be written as a sum of three ...

422 = 2 x 211. 422 is 222 in base 14. It is 646 in base 8. 422 is the maximum number of regions into which 21 circles divide the plane. 422...

100 = 2 2 x 5 2 . 100 has a representation as a sum of two squares: 100 = 6 2 + 8 2 . 100 is the sum of the first four cubes: 100 = 1 3 +...

1316 = 2 2 x 7 x 47. 1316 = 6 4 + 20. 1316 is 2444 in base 8. 1316 is a number divisible by the sum of the squares of its digits: 1 2 + 3...

167 is a prime number. 167 cannot be written as a sum of three squares. 167 is the smallest number whose fourth power begins with four iden...

842 = 2 x 421. 842 has a representation as a sum of two squares: 842 = 1 2 + 29 2 . 842 is a semiprime sandwiched between semiprimes: 841 =...

474 = 2 x 3 x 79. 474 is a nonagonal number . 474 is a member of the Fibonacci-like sequence starting with 1 and 8: 1, 8, 9, 17, 26, 43, 69,...

820 = 2 2 x 5 x 41. 820 has two representations as a sum of two squares: 820 = 6 2 + 28 2 = 12 2 + 26 2 . 820 is the 40th triangular num...

215 = 5 x 43. 215 is a number that cannot be written as a sum of three squares. 215 is 3113 in base 4 and 555 in base 6. 215 3 = 9,938,375 ...

158 = 2 x 79. 158 is the maximum number of regions into which 13 circles divide the plane. 158 is the smallest number such that the sum of t...

891 = 3 4 x 11. 891 is an octahedral number . 891 is the smallest number that is the reversal of the sum of its proper substrings: 8 + 9 +...

69 = 3 x 23. 69 = 9 + 10 + 11 + 12 + 13 + 14. 69 is the only number whose square and cube together use all the digits from 0 to 9: 69 2 = ...