640665908 has 24 divisors (see below), whose sum is σ = 1143942912. Its totient is φ = 313842464.

The previous prime is 640665899. The next prime is 640665911. The reversal of 640665908 is 809566046.

640665908 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

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, 186341 + ... + 189747.

It is an arithmetic number, because the mean of its divisors is an integer number (47664288).

Almost surely, 2^640665908 is an apocalyptic number.

It is an amenable number.

640665908 is a deficient number, since it is larger than the sum of its proper divisors (503277004).

640665908 is a wasteful number, since it uses less digits than its factorization.

640665908 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4351 (or 4349 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 44.

The square root of 640665908 is about 25311.3790220920. The cubic root of 640665908 is about 862.0726589306.

The spelling of 640665908 in words is "six hundred forty million, six hundred sixty-five thousand, nine hundred eight".