639680 has 28 divisors (see below), whose sum is σ = 1524000. Its totient is φ = 255744.

The previous prime is 639679. The next prime is 639689. The reversal of 639680 is 86936.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is not an unprimeable number, because it can be changed into a prime (639689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 680 + ... + 1319.

2⁶³⁹⁶⁸⁰ is an apocalyptic number.

It is an amenable number.

639680 is an abundant number, since it is smaller than the sum of its proper divisors (884320).

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

639680 is a wasteful number, since it uses less digits than its factorization.

639680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2016 (or 2006 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 32.

The square root of 639680 is about 799.7999749937. The cubic root of 639680 is about 86.1630223089.

The spelling of 639680 in words is "six hundred thirty-nine thousand, six hundred eighty".