256508921 has 2 divisors, whose sum is σ = 256508922. Its totient is φ = 256508920.

The previous prime is 256508909. The next prime is 256508929. The reversal of 256508921 is 129805652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 243984400 + 12524521 = 15620^2 + 3539^2 .

It is a cyclic number.

It is not a de Polignac number, because 256508921 - 2¹⁰ = 256507897 is a prime.

It is not a weakly prime, because it can be changed into another prime (256508929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128254460 + 128254461.

It is an arithmetic number, because the mean of its divisors is an integer number (128254461).

Almost surely, 2^256508921 is an apocalyptic number.

It is an amenable number.

256508921 is a deficient number, since it is larger than the sum of its proper divisors (1).

256508921 is an equidigital number, since it uses as much as digits as its factorization.

256508921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 43200, while the sum is 38.

The square root of 256508921 is about 16015.8958850262. The cubic root of 256508921 is about 635.3809035923.

The spelling of 256508921 in words is "two hundred fifty-six million, five hundred eight thousand, nine hundred twenty-one".