644764688 has 40 divisors (see below), whose sum is σ = 1282417920. Its totient is φ = 313852160.

The previous prime is 644764669. The next prime is 644764699. The reversal of 644764688 is 886467446.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 470981 + ... + 472347.

It is an arithmetic number, because the mean of its divisors is an integer number (32060448).

Almost surely, 2^644764688 is an apocalyptic number.

It is an amenable number.

644764688 is a deficient number, since it is larger than the sum of its proper divisors (637653232).

644764688 is a wasteful number, since it uses less digits than its factorization.

644764688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2135 (or 2129 counting only the distinct ones).

The product of its digits is 6193152, while the sum is 53.

The square root of 644764688 is about 25392.2170753166. The cubic root of 644764688 is about 863.9071759560.

The spelling of 644764688 in words is "six hundred forty-four million, seven hundred sixty-four thousand, six hundred eighty-eight".