256638 has 8 divisors (see below), whose sum is σ = 513288. Its totient is φ = 85544.

The previous prime is 256609. The next prime is 256639. The reversal of 256638 is 836652.

It is a sphenic number, since it is the product of 3 distinct primes.

256638 is an admirable number.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 256638.

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, 21381 + ... + 21392.

It is an arithmetic number, because the mean of its divisors is an integer number (64161).

2²⁵⁶⁶³⁸ is an apocalyptic number.

256638 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

256638 is a wasteful number, since it uses less digits than its factorization.

256638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42778.

The product of its digits is 8640, while the sum is 30.

The square root of 256638 is about 506.5945124061. The cubic root of 256638 is about 63.5487463341.

The spelling of 256638 in words is "two hundred fifty-six thousand, six hundred thirty-eight".