640657816 has 8 divisors (see below), whose sum is σ = 1201233420. Its totient is φ = 320328904.

The previous prime is 640657783. The next prime is 640657859. The reversal of 640657816 is 618756046.

It is a happy number.

640657816 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40041106 + ... + 40041121.

Almost surely, 2^640657816 is an apocalyptic number.

It is an amenable number.

640657816 is a deficient number, since it is larger than the sum of its proper divisors (560575604).

640657816 is a wasteful number, since it uses less digits than its factorization.

640657816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80082233 (or 80082229 counting only the distinct ones).

The product of its (nonzero) digits is 241920, while the sum is 43.

The square root of 640657816 is about 25311.2191725330. The cubic root of 640657816 is about 862.0690294147.

The spelling of 640657816 in words is "six hundred forty million, six hundred fifty-seven thousand, eight hundred sixteen".