640393636 has 9 divisors (see below), whose sum is σ = 1120777441. Its totient is φ = 320171512.

The previous prime is 640393603. The next prime is 640393657. The reversal of 640393636 is 636393046.

The square root of 640393636 is 25306.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 2528100 + 637865536 = 1590^2 + 25256^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 44286 + ... + 56938.

Almost surely, 2^640393636 is an apocalyptic number.

640393636 is the 25306-th square number.

It is an amenable number.

640393636 is a deficient number, since it is larger than the sum of its proper divisors (480383805).

640393636 is an frugal number, since it uses more digits than its factorization.

640393636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25310 (or 12655 counting only the distinct ones).

The product of its (nonzero) digits is 209952, while the sum is 40.

The cubic root of 640393636 is about 861.9505196053.

The spelling of 640393636 in words is "six hundred forty million, three hundred ninety-three thousand, six hundred thirty-six".