256643644 has 24 divisors (see below), whose sum is σ = 453454848. Its totient is φ = 127091760.

The previous prime is 256643627. The next prime is 256643669. The reversal of 256643644 is 446346652.

It is a junction number, because it is equal to n+sod(n) for n = 256643597 and 256643606.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 215619 + ... + 216805.

It is an arithmetic number, because the mean of its divisors is an integer number (18893952).

Almost surely, 2^256643644 is an apocalyptic number.

It is an amenable number.

256643644 is a deficient number, since it is larger than the sum of its proper divisors (196811204).

256643644 is a wasteful number, since it uses less digits than its factorization.

256643644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1665 (or 1663 counting only the distinct ones).

The product of its digits is 414720, while the sum is 40.

The square root of 256643644 is about 16020.1012481195. The cubic root of 256643644 is about 635.4921218678.

The spelling of 256643644 in words is "two hundred fifty-six million, six hundred forty-three thousand, six hundred forty-four".