640494864 has 225 divisors, whose sum is σ = 2010787317. Its totient is φ = 196795008.

The previous prime is 640494817. The next prime is 640494913. The reversal of 640494864 is 468494046.

The square root of 640494864 is 25308.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 573123600 + 67371264 = 23940^2 + 8208^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 17310654 + ... + 17310690.

Almost surely, 2^640494864 is an apocalyptic number.

640494864 is the 25308-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640494864

640494864 is an abundant number, since it is smaller than the sum of its proper divisors (1370292453).

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

640494864 is a wasteful number, since it uses less digits than its factorization.

640494864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132 (or 61 counting only the distinct ones).

The product of its (nonzero) digits is 663552, while the sum is 45.

The cubic root of 640494864 is about 861.9959338241.

The spelling of 640494864 in words is "six hundred forty million, four hundred ninety-four thousand, eight hundred sixty-four".