640493388 has 18 divisors (see below), whose sum is σ = 1619025044. Its totient is φ = 213497784.

The previous prime is 640493353. The next prime is 640493389. The reversal of 640493388 is 883394046.

It is a tau number, because it is divible by the number of its divisors (18).

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (640493389) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8895706 + ... + 8895777.

Almost surely, 2^640493388 is an apocalyptic number.

It is an amenable number.

640493388 is an abundant number, since it is smaller than the sum of its proper divisors (978531656).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640493388 is a wasteful number, since it uses less digits than its factorization.

640493388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17791493 (or 17791488 counting only the distinct ones).

The product of its (nonzero) digits is 497664, while the sum is 45.

The square root of 640493388 is about 25307.9708392435. The cubic root of 640493388 is about 861.9952716762.

The spelling of 640493388 in words is "six hundred forty million, four hundred ninety-three thousand, three hundred eighty-eight".