640397992 has 16 divisors (see below), whose sum is σ = 1293111540. Its totient is φ = 295568256.

The previous prime is 640397963. The next prime is 640398023. The reversal of 640397992 is 299793046.

It can be written as a sum of positive squares in 2 ways, for example, as 640393636 + 4356 = 25306^2 + 66^2 .

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, 3078733 + ... + 3078940.

Almost surely, 2^640397992 is an apocalyptic number.

It is an amenable number.

640397992 is an abundant number, since it is smaller than the sum of its proper divisors (652713548).

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

640397992 is a wasteful number, since it uses less digits than its factorization.

640397992 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6157692 (or 6157688 counting only the distinct ones).

The product of its (nonzero) digits is 734832, while the sum is 49.

The square root of 640397992 is about 25306.0860663991. The cubic root of 640397992 is about 861.9524739491.

The spelling of 640397992 in words is "six hundred forty million, three hundred ninety-seven thousand, nine hundred ninety-two".