644766656 has 28 divisors (see below), whose sum is σ = 1310670480. Its totient is φ = 314519040.

The previous prime is 644766643. The next prime is 644766671. The reversal of 644766656 is 656667446.

644766656 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

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, 120236 + ... + 125483.

It is an arithmetic number, because the mean of its divisors is an integer number (46809660).

Almost surely, 2^644766656 is an apocalyptic number.

It is an amenable number.

644766656 is an abundant number, since it is smaller than the sum of its proper divisors (665903824).

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

644766656 is a wasteful number, since it uses less digits than its factorization.

644766656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245772 (or 245762 counting only the distinct ones).

The product of its digits is 4354560, while the sum is 50.

The square root of 644766656 is about 25392.2558273187. The cubic root of 644766656 is about 863.9080549162.

The spelling of 644766656 in words is "six hundred forty-four million, seven hundred sixty-six thousand, six hundred fifty-six".