640891108 has 48 divisors (see below), whose sum is σ = 1321729920. Its totient is φ = 268070400.

The previous prime is 640891091. The next prime is 640891123. The reversal of 640891108 is 801198046.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 203788 + ... + 206908.

It is an arithmetic number, because the mean of its divisors is an integer number (27536040).

Almost surely, 2^640891108 is an apocalyptic number.

It is an amenable number.

640891108 is an abundant number, since it is smaller than the sum of its proper divisors (680838812).

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

640891108 is a wasteful number, since it uses less digits than its factorization.

640891108 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3508 (or 3506 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 37.

The square root of 640891108 is about 25315.8272233004. The cubic root of 640891108 is about 862.1736559389.

The spelling of 640891108 in words is "six hundred forty million, eight hundred ninety-one thousand, one hundred eight".