644926636 has 6 divisors (see below), whose sum is σ = 1128621620. Its totient is φ = 322463316.

The previous prime is 644926591. The next prime is 644926649. The reversal of 644926636 is 636629446.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80615826 + ... + 80615833.

Almost surely, 2^644926636 is an apocalyptic number.

It is an amenable number.

644926636 is a deficient number, since it is larger than the sum of its proper divisors (483694984).

644926636 is a wasteful number, since it uses less digits than its factorization.

644926636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161231663 (or 161231661 counting only the distinct ones).

The product of its digits is 1119744, while the sum is 46.

The square root of 644926636 is about 25395.4058049876. The cubic root of 644926636 is about 863.9795001852.

The spelling of 644926636 in words is "six hundred forty-four million, nine hundred twenty-six thousand, six hundred thirty-six".