639944 has 16 divisors (see below), whose sum is σ = 1209600. Its totient is φ = 317392.

The previous prime is 639941. The next prime is 639949. The reversal of 639944 is 449936.

It is a happy number.

Its product of digits (23328) is a multiple of the sum of its prime divisors (648).

It is not an unprimeable number, because it can be changed into a prime (639941) 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, 1097 + ... + 1575.

It is an arithmetic number, because the mean of its divisors is an integer number (75600).

2⁶³⁹⁹⁴⁴ is an apocalyptic number.

It is an amenable number.

639944 is a deficient number, since it is larger than the sum of its proper divisors (569656).

639944 is a wasteful number, since it uses less digits than its factorization.

639944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 652 (or 648 counting only the distinct ones).

The product of its digits is 23328, while the sum is 35.

The square root of 639944 is about 799.9649992343. The cubic root of 639944 is about 86.1748740208.

Subtracting from 639944 its product of digits (23328), we obtain a palindrome (616616).

The spelling of 639944 in words is "six hundred thirty-nine thousand, nine hundred forty-four".