640643680 has 24 divisors (see below), whose sum is σ = 1513521072. Its totient is φ = 256257408.

The previous prime is 640643671. The next prime is 640643719. The reversal of 640643680 is 86346046.

It is a congruent number.

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, 2001852 + ... + 2002171.

It is an arithmetic number, because the mean of its divisors is an integer number (63063378).

Almost surely, 2^640643680 is an apocalyptic number.

It is an amenable number.

640643680 is an abundant number, since it is smaller than the sum of its proper divisors (872877392).

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

640643680 is a wasteful number, since it uses less digits than its factorization.

640643680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4004038 (or 4004030 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 37.

The square root of 640643680 is about 25310.9399272330. The cubic root of 640643680 is about 862.0626889018.

It can be divided in two parts, 6406 and 43680, that added together give a triangular number (50086 = T₃₁₆).

The spelling of 640643680 in words is "six hundred forty million, six hundred forty-three thousand, six hundred eighty".