644686774680 has 64 divisors (see below), whose sum is σ = 2082834200160. Its totient is φ = 158692128768.

The previous prime is 644686774679. The next prime is 644686774717. The reversal of 644686774680 is 86477686446.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 206628817 + ... + 206631936.

Almost surely, 2^644686774680 is an apocalyptic number.

644686774680 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644686774680 is an abundant number, since it is smaller than the sum of its proper divisors (1438147425480).

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

644686774680 is a wasteful number, since it uses less digits than its factorization.

644686774680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 413260780 (or 413260776 counting only the distinct ones).

The product of its (nonzero) digits is 260112384, while the sum is 66.

The spelling of 644686774680 in words is "six hundred forty-four billion, six hundred eighty-six million, seven hundred seventy-four thousand, six hundred eighty".