644644551016 has 8 divisors (see below), whose sum is σ = 1208708533170. Its totient is φ = 322322275504.

The previous prime is 644644550993. The next prime is 644644551043. The reversal of 644644551016 is 610155446446.

It can be written as a sum of positive squares in only one way, i.e., 507784508100 + 136860042916 = 712590^2 + 369946^2 .

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, 40290284431 + ... + 40290284446.

Almost surely, 2^644644551016 is an apocalyptic number.

It is an amenable number.

644644551016 is a deficient number, since it is larger than the sum of its proper divisors (564063982154).

644644551016 is a wasteful number, since it uses less digits than its factorization.

644644551016 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80580568883 (or 80580568879 counting only the distinct ones).

The product of its (nonzero) digits is 1382400, while the sum is 46.

The spelling of 644644551016 in words is "six hundred forty-four billion, six hundred forty-four million, five hundred fifty-one thousand, sixteen".