256564639 has 2 divisors, whose sum is σ = 256564640. Its totient is φ = 256564638.

The previous prime is 256564631. The next prime is 256564667. The reversal of 256564639 is 936465652.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 256564639 - 2³ = 256564631 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256564631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128282319 + 128282320.

It is an arithmetic number, because the mean of its divisors is an integer number (128282320).

Almost surely, 2^256564639 is an apocalyptic number.

256564639 is a deficient number, since it is larger than the sum of its proper divisors (1).

256564639 is an equidigital number, since it uses as much as digits as its factorization.

256564639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1166400, while the sum is 46.

The square root of 256564639 is about 16017.6352499362. The cubic root of 256564639 is about 635.4269053584.

The spelling of 256564639 in words is "two hundred fifty-six million, five hundred sixty-four thousand, six hundred thirty-nine".