640044639 has 16 divisors (see below), whose sum is σ = 1021154400. Its totient is φ = 393873408.

The previous prime is 640044617. The next prime is 640044641. The reversal of 640044639 is 936440046.

640044639 is a `hidden beast` number, since 640 + 0 + 4 + 4 + 6 + 3 + 9 = 666.

It is not a de Polignac number, because 640044639 - 2⁵ = 640044607 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640044689) 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, 911394 + ... + 912095.

It is an arithmetic number, because the mean of its divisors is an integer number (63822150).

Almost surely, 2^640044639 is an apocalyptic number.

640044639 is a deficient number, since it is larger than the sum of its proper divisors (381109761).

640044639 is a wasteful number, since it uses less digits than its factorization.

640044639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1823511 (or 1823505 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 36.

The square root of 640044639 is about 25299.1035216665. The cubic root of 640044639 is about 861.7939113407.

The spelling of 640044639 in words is "six hundred forty million, forty-four thousand, six hundred thirty-nine".