640794256 has 20 divisors (see below), whose sum is σ = 1270413232. Its totient is φ = 312945696.

The previous prime is 640794251. The next prime is 640794257. The reversal of 640794256 is 652497046.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (43).

It is not an unprimeable number, because it can be changed into a prime (640794251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 465006 + ... + 466381.

Almost surely, 2^640794256 is an apocalyptic number.

It is an amenable number.

640794256 is a deficient number, since it is larger than the sum of its proper divisors (629618976).

640794256 is a wasteful number, since it uses less digits than its factorization.

640794256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 931438 (or 931432 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 43.

The square root of 640794256 is about 25313.9142765397. The cubic root of 640794256 is about 862.1302229497.

The spelling of 640794256 in words is "six hundred forty million, seven hundred ninety-four thousand, two hundred fifty-six".