639820 has 12 divisors (see below), whose sum is σ = 1343664. Its totient is φ = 255920.

The previous prime is 639757. The next prime is 639833. The reversal of 639820 is 28936.

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, 15976 + ... + 16015.

It is an arithmetic number, because the mean of its divisors is an integer number (111972).

2⁶³⁹⁸²⁰ is an apocalyptic number.

It is an amenable number.

639820 is an abundant number, since it is smaller than the sum of its proper divisors (703844).

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

639820 is a wasteful number, since it uses less digits than its factorization.

639820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32000 (or 31998 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 28.

The square root of 639820 is about 799.8874920887. The cubic root of 639820 is about 86.1693077137.

The spelling of 639820 in words is "six hundred thirty-nine thousand, eight hundred twenty".