640644392 has 24 divisors (see below), whose sum is σ = 1255713690. Its totient is φ = 306393120.

The previous prime is 640644383. The next prime is 640644397. The reversal of 640644392 is 293446046.

640644392 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 548215396 + 92428996 = 23414^2 + 9614^2 .

It is not an unprimeable number, because it can be changed into a prime (640644397) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 71459 + ... + 79922.

Almost surely, 2^640644392 is an apocalyptic number.

It is an amenable number.

640644392 is a deficient number, since it is larger than the sum of its proper divisors (615069298).

640644392 is a wasteful number, since it uses less digits than its factorization.

640644392 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151433 (or 151406 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 38.

The square root of 640644392 is about 25310.9539922935. The cubic root of 640644392 is about 862.0630082621.

The spelling of 640644392 in words is "six hundred forty million, six hundred forty-four thousand, three hundred ninety-two".