256564055491 has 2 divisors, whose sum is σ = 256564055492. Its totient is φ = 256564055490.

The previous prime is 256564055453. The next prime is 256564055497. The reversal of 256564055491 is 194550465652.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 256564055491 - 2¹¹ = 256564053443 is a prime.

It is a super-2 number, since 2×256564055491² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (256564055497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128282027745 + 128282027746.

It is an arithmetic number, because the mean of its divisors is an integer number (128282027746).

Almost surely, 2^256564055491 is an apocalyptic number.

256564055491 is a deficient number, since it is larger than the sum of its proper divisors (1).

256564055491 is an equidigital number, since it uses as much as digits as its factorization.

256564055491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6480000, while the sum is 52.

The spelling of 256564055491 in words is "two hundred fifty-six billion, five hundred sixty-four million, fifty-five thousand, four hundred ninety-one".