640403968 has 40 divisors (see below), whose sum is σ = 1346922720. Its totient is φ = 303344640.

The previous prime is 640403909. The next prime is 640403989. The reversal of 640403968 is 869304046.

It is a self number, because there is not a number n which added to its sum of digits gives 640403968.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23188 + ... + 42643.

It is an arithmetic number, because the mean of its divisors is an integer number (33673068).

Almost surely, 2^640403968 is an apocalyptic number.

It is an amenable number.

640403968 is an abundant number, since it is smaller than the sum of its proper divisors (706518752).

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

640403968 is an equidigital number, since it uses as much as digits as its factorization.

640403968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65868 (or 65852 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 40.

The square root of 640403968 is about 25306.2041404870. The cubic root of 640403968 is about 861.9551551005.

The spelling of 640403968 in words is "six hundred forty million, four hundred three thousand, nine hundred sixty-eight".