# 487

This number is a prime.

A prime *p* such that the decimal fraction 1/*p* has the same period length as 1/*p*^{2}. [Richter]

487^{2} divides 10^{486} - 1.

487 is the smallest prime *p* such that *p* and *p*^{3} have the same sum of digits. [Honaker]

There are 487 Hadamard matrices of order 28. Note that 28 is a perfect number. [Rupinski]

487 = (4!_{2} + 8!_{2} + 7!_{2}) - (π(4) + π(8) + π(7)). Note that 487 is the smallest prime with this property. [Firoozbakht]

Fermat claimed (correctly) that a number is the sum of three squares unless it is of the form 4^{n}(8*m* + 7), with n,m greater than or equal to 0.

487 is the first prime after 3 that divides the periodic part of the decimal representation of its reciprocal. [Noe]

The Demilitarized Zone (DMZ) is 487 square miles.

487!+491 is the first titanic prime of form p!+q where p, q are consecutive primes. [Loungrides]

The smallest of five consecutive full period primes (487, 491, 499, 503, 509). [Bowser]

The smallest prime p such that all possible two-digit endings for prime numbers less than or equal to p occur at least once. [Honaker]

The smallest prime number that produces three more primes when reiteratively doubled and reversed three consecutive times (479, 859, and 8171). [Gaydos]

The smallest prime p such that reversal(2p) equals its previous prime. [Bajpai]

487 is the largest prime in a set of primes (26) that has at least one "1", two "2s", … , "nine "9s" with a minimal of the largest of these primes: {5, 19, 29, 41, 47, 53, 59, 61, 67, 79, 83, 89, 97, 149, 151, 157, 163, 167, 181, 263, 269, 281, 283, 383, 389, 487}. By Giovanni Resta. [Rivera]

There's a 487-steps trail on the Qingming Farm in Taiwan.

There are 487 "one pair" Sophie Germain primes; 5-digit numbers with 4 different digits. [Gaydos]