644988976 has 40 divisors (see below), whose sum is σ = 1365876864. Its totient is φ = 293729280.

The previous prime is 644988961. The next prime is 644988983. The reversal of 644988976 is 679889446.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29815 + ... + 46678.

Almost surely, 2^644988976 is an apocalyptic number.

It is an amenable number.

644988976 is an abundant number, since it is smaller than the sum of its proper divisors (720887888).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644988976 is a wasteful number, since it uses less digits than its factorization.

644988976 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76549 (or 76543 counting only the distinct ones).

The product of its digits is 20901888, while the sum is 61.

The square root of 644988976 is about 25396.6331626852. The cubic root of 644988976 is about 864.0073373291.

The spelling of 644988976 in words is "six hundred forty-four million, nine hundred eighty-eight thousand, nine hundred seventy-six".