644455563656 has 16 divisors (see below), whose sum is σ = 1215030174540. Its totient is φ = 320447517120.

The previous prime is 644455563611. The next prime is 644455563671. The reversal of 644455563656 is 656365554446.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 495945526756 + 148510036900 = 704234^2 + 385370^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644455563595 and 644455563604.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 222531551 + ... + 222534446.

Almost surely, 2^644455563656 is an apocalyptic number.

It is an amenable number.

644455563656 is a deficient number, since it is larger than the sum of its proper divisors (570574610884).

644455563656 is a wasteful number, since it uses less digits than its factorization.

644455563656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 445066184 (or 445066180 counting only the distinct ones).

The product of its digits is 155520000, while the sum is 59.

The spelling of 644455563656 in words is "six hundred forty-four billion, four hundred fifty-five million, five hundred sixty-three thousand, six hundred fifty-six".