644022636 has 24 divisors (see below), whose sum is σ = 1503237120. Its totient is φ = 214600272.

The previous prime is 644022581. The next prime is 644022649. The reversal of 644022636 is 636220446.

It is a junction number, because it is equal to n+sod(n) for n = 644022597 and 644022606.

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, 35845 + ... + 50723.

It is an arithmetic number, because the mean of its divisors is an integer number (62634880).

Almost surely, 2^644022636 is an apocalyptic number.

It is an amenable number.

644022636 is an abundant number, since it is smaller than the sum of its proper divisors (859214484).

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

644022636 is a wasteful number, since it uses less digits than its factorization.

644022636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18493 (or 18491 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 33.

The square root of 644022636 is about 25377.6010686590. The cubic root of 644022636 is about 863.5756285724.

The spelling of 644022636 in words is "six hundred forty-four million, twenty-two thousand, six hundred thirty-six".