644252914856 has 8 divisors (see below), whose sum is σ = 1207974215370. Its totient is φ = 322126457424.

The previous prime is 644252914847. The next prime is 644252914867. The reversal of 644252914856 is 658419252446.

It can be written as a sum of positive squares in only one way, i.e., 438469108900 + 205783805956 = 662170^2 + 453634^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40265807171 + ... + 40265807186.

Almost surely, 2^644252914856 is an apocalyptic number.

It is an amenable number.

644252914856 is a deficient number, since it is larger than the sum of its proper divisors (563721300514).

644252914856 is a wasteful number, since it uses less digits than its factorization.

644252914856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80531614363 (or 80531614359 counting only the distinct ones).

The product of its digits is 16588800, while the sum is 56.

The spelling of 644252914856 in words is "six hundred forty-four billion, two hundred fifty-two million, nine hundred fourteen thousand, eight hundred fifty-six".