256339921 has 2 divisors, whose sum is σ = 256339922. Its totient is φ = 256339920.

The previous prime is 256339901. The next prime is 256339969. The reversal of 256339921 is 129933652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 252969025 + 3370896 = 15905^2 + 1836^2 .

It is a cyclic number.

It is not a de Polignac number, because 256339921 - 2¹⁵ = 256307153 is a prime.

It is not a weakly prime, because it can be changed into another prime (256339901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128169960 + 128169961.

It is an arithmetic number, because the mean of its divisors is an integer number (128169961).

Almost surely, 2^256339921 is an apocalyptic number.

It is an amenable number.

256339921 is a deficient number, since it is larger than the sum of its proper divisors (1).

256339921 is an equidigital number, since it uses as much as digits as its factorization.

256339921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 87480, while the sum is 40.

The square root of 256339921 is about 16010.6190073963. The cubic root of 256339921 is about 635.2413334451.

The spelling of 256339921 in words is "two hundred fifty-six million, three hundred thirty-nine thousand, nine hundred twenty-one".