639968 has 24 divisors (see below), whose sum is σ = 1440432. Its totient is φ = 274176.

The previous prime is 639959. The next prime is 639983. The reversal of 639968 is 869936.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1205 + ... + 1652.

It is an arithmetic number, because the mean of its divisors is an integer number (60018).

2⁶³⁹⁹⁶⁸ is an apocalyptic number.

It is an amenable number.

639968 is an abundant number, since it is smaller than the sum of its proper divisors (800464).

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

639968 is a wasteful number, since it uses less digits than its factorization.

639968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2874 (or 2866 counting only the distinct ones).

The product of its digits is 69984, while the sum is 41.

The square root of 639968 is about 799.9799997500. The cubic root of 639968 is about 86.1759512875.

The spelling of 639968 in words is "six hundred thirty-nine thousand, nine hundred sixty-eight".