640644393 has 16 divisors (see below), whose sum is σ = 879592896. Its totient is φ = 414504960.

The previous prime is 640644383. The next prime is 640644397. The reversal of 640644393 is 393446046.

It is a happy number.

It is not a de Polignac number, because 640644393 - 2⁴ = 640644377 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640644397) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10246 + ... + 37232.

It is an arithmetic number, because the mean of its divisors is an integer number (54974556).

Almost surely, 2^640644393 is an apocalyptic number.

It is an amenable number.

640644393 is a deficient number, since it is larger than the sum of its proper divisors (238948503).

640644393 is a wasteful number, since it uses less digits than its factorization.

640644393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27224.

The product of its (nonzero) digits is 186624, while the sum is 39.

The square root of 640644393 is about 25310.9540120478. The cubic root of 640644393 is about 862.0630087106.

The spelling of 640644393 in words is "six hundred forty million, six hundred forty-four thousand, three hundred ninety-three".