644707976128 has 28 divisors (see below), whose sum is σ = 1320611503552. Its totient is φ = 311955471360.

The previous prime is 644707976089. The next prime is 644707976177. The reversal of 644707976128 is 821679707446.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 162474825 + ... + 162478792.

Almost surely, 2^644707976128 is an apocalyptic number.

It is an amenable number.

644707976128 is an abundant number, since it is smaller than the sum of its proper divisors (675903527424).

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

644707976128 is a wasteful number, since it uses less digits than its factorization.

644707976128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 324953660 (or 324953650 counting only the distinct ones).

The product of its (nonzero) digits is 28449792, while the sum is 61.

The spelling of 644707976128 in words is "six hundred forty-four billion, seven hundred seven million, nine hundred seventy-six thousand, one hundred twenty-eight".