640991232 has 360 divisors, whose sum is σ = 2290020096. Its totient is φ = 175177728.

The previous prime is 640991191. The next prime is 640991249. The reversal of 640991232 is 232199046.

640991232 is a `hidden beast` number, since 640 + 9 + 9 + 1 + 2 + 3 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27869173 + ... + 27869195.

Almost surely, 2^640991232 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640991232, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1145010048).

640991232 is an abundant number, since it is smaller than the sum of its proper divisors (1649028864).

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

640991232 is an frugal number, since it uses more digits than its factorization.

640991232 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73 (or 35 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 36.

The square root of 640991232 is about 25317.8046441630. The cubic root of 640991232 is about 862.2185516469.

The spelling of 640991232 in words is "six hundred forty million, nine hundred ninety-one thousand, two hundred thirty-two".