639980 has 24 divisors (see below), whose sum is σ = 1466640. Its totient is φ = 232640.

The previous prime is 639959. The next prime is 639983. The reversal of 639980 is 89936.

It is a nialpdrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 639980.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639980.

It is not an unprimeable number, because it can be changed into a prime (639983) by changing a digit.

639980 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1235 + ... + 1674.

It is an arithmetic number, because the mean of its divisors is an integer number (61110).

2⁶³⁹⁹⁸⁰ is an apocalyptic number.

It is an amenable number.

639980 is an abundant number, since it is smaller than the sum of its proper divisors (826660).

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

639980 is a wasteful number, since it uses less digits than its factorization.

639980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2929 (or 2927 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 639980 is about 799.9874999023. The cubic root of 639980 is about 86.1764899108.

The spelling of 639980 in words is "six hundred thirty-nine thousand, nine hundred eighty".