640386956 has 24 divisors (see below), whose sum is σ = 1238039040. Its totient is φ = 287398800.

The previous prime is 640386949. The next prime is 640386977. The reversal of 640386956 is 659683046.

It is a self number, because there is not a number n which added to its sum of digits gives 640386956.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 88640 + ... + 95591.

It is an arithmetic number, because the mean of its divisors is an integer number (51584960).

Almost surely, 2^640386956 is an apocalyptic number.

It is an amenable number.

640386956 is a deficient number, since it is larger than the sum of its proper divisors (597652084).

640386956 is a wasteful number, since it uses less digits than its factorization.

640386956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184325 (or 184323 counting only the distinct ones).

The product of its (nonzero) digits is 933120, while the sum is 47.

The square root of 640386956 is about 25305.8680151462. The cubic root of 640386956 is about 861.9475225687.

The spelling of 640386956 in words is "six hundred forty million, three hundred eighty-six thousand, nine hundred fifty-six".