639780 has 24 divisors (see below), whose sum is σ = 1791552. Its totient is φ = 170592.

The previous prime is 639757. The next prime is 639833. The reversal of 639780 is 87936.

It is a happy number.

It is an Ulam number.

It is a nialpdrome in base 15.

It is an unprimeable number.

639780 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5272 + ... + 5391.

It is an arithmetic number, because the mean of its divisors is an integer number (74648).

2⁶³⁹⁷⁸⁰ is an apocalyptic number.

639780 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

639780 is an abundant number, since it is smaller than the sum of its proper divisors (1151772).

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

639780 is a wasteful number, since it uses less digits than its factorization.

639780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10675 (or 10673 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 33.

The square root of 639780 is about 799.8624881816. The cubic root of 639780 is about 86.1675119773.

The spelling of 639780 in words is "six hundred thirty-nine thousand, seven hundred eighty".