256631 has 4 divisors (see below), whose sum is σ = 257712. Its totient is φ = 255552.

The previous prime is 256609. The next prime is 256639. The reversal of 256631 is 136652.

256631 is nontrivially palindromic in base 6.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 256631 - 2⁶ = 256567 is a prime.

It is a super-2 number, since 2×256631² = 131718940322, which contains 22 as substring.

It is a Duffinian number.

Its product of digits (1080) is a multiple of the sum of its prime divisors (1080).

It is a junction number, because it is equal to n+sod(n) for n = 256597 and 256606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256639) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11 + ... + 716.

It is an arithmetic number, because the mean of its divisors is an integer number (64428).

2²⁵⁶⁶³¹ is an apocalyptic number.

256631 is a deficient number, since it is larger than the sum of its proper divisors (1081).

256631 is an equidigital number, since it uses as much as digits as its factorization.

256631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1080.

The product of its digits is 1080, while the sum is 23.

The square root of 256631 is about 506.5876034804. The cubic root of 256631 is about 63.5481685484.

The spelling of 256631 in words is "two hundred fifty-six thousand, six hundred thirty-one".