644792816 has 20 divisors (see below), whose sum is σ = 1315038600. Its totient is φ = 305428032.

The previous prime is 644792761. The next prime is 644792831. The reversal of 644792816 is 618297446.

644792816 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, 1060211 + ... + 1060818.

It is an arithmetic number, because the mean of its divisors is an integer number (65751930).

Almost surely, 2^644792816 is an apocalyptic number.

It is an amenable number.

644792816 is an abundant number, since it is smaller than the sum of its proper divisors (670245784).

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

644792816 is a wasteful number, since it uses less digits than its factorization.

644792816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2121056 (or 2121050 counting only the distinct ones).

The product of its digits is 580608, while the sum is 47.

The square root of 644792816 is about 25392.7709397773. The cubic root of 644792816 is about 863.9197384862.

The spelling of 644792816 in words is "six hundred forty-four million, seven hundred ninety-two thousand, eight hundred sixteen".