256921 has 12 divisors (see below), whose sum is σ = 314368. Its totient is φ = 205632.

The previous prime is 256903. The next prime is 256931. The reversal of 256921 is 129652.

It is not a de Polignac number, because 256921 - 2⁵ = 256889 is a prime.

It is a hoax number, since the sum of its digits (25) coincides with the sum of the digits of its distinct prime factors.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256901) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1960 + ... + 2086.

2²⁵⁶⁹²¹ is an apocalyptic number.

It is an amenable number.

256921 is a deficient number, since it is larger than the sum of its proper divisors (57447).

256921 is a wasteful number, since it uses less digits than its factorization.

256921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168 (or 151 counting only the distinct ones).

The product of its digits is 1080, while the sum is 25.

The square root of 256921 is about 506.8737515398. The cubic root of 256921 is about 63.5720965897.

The spelling of 256921 in words is "two hundred fifty-six thousand, nine hundred twenty-one".