487
This number is a prime.
A prime p such that the decimal fraction 1/p has the same period length as 1/p2. [Richter]
4872 divides 10486 - 1.
487 is the smallest prime p such that p and p3 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 4n(8m + 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]