644693640 has 64 divisors (see below), whose sum is σ = 1937640960. Its totient is φ = 171601920.

The previous prime is 644693633. The next prime is 644693681. The reversal of 644693640 is 46396446.

644693640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a junction number, because it is equal to n+sod(n) for n = 644693592 and 644693601.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 64585 + ... + 73895.

It is an arithmetic number, because the mean of its divisors is an integer number (30275640).

Almost surely, 2^644693640 is an apocalyptic number.

644693640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644693640 is an abundant number, since it is smaller than the sum of its proper divisors (1292947320).

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

644693640 is a wasteful number, since it uses less digits than its factorization.

644693640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9902 (or 9898 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 42.

The square root of 644693640 is about 25390.8180254201. The cubic root of 644693640 is about 863.8754428639.

The spelling of 644693640 in words is "six hundred forty-four million, six hundred ninety-three thousand, six hundred forty".