639878 has 8 divisors (see below), whose sum is σ = 985872. Its totient is φ = 311256.

The previous prime is 639857. The next prime is 639907. The reversal of 639878 is 878936.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639878.

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, 4250 + ... + 4397.

It is an arithmetic number, because the mean of its divisors is an integer number (123234).

2⁶³⁹⁸⁷⁸ is an apocalyptic number.

639878 is a deficient number, since it is larger than the sum of its proper divisors (345994).

639878 is a wasteful number, since it uses less digits than its factorization.

639878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8686.

The product of its digits is 72576, while the sum is 41.

The square root of 639878 is about 799.9237463659. The cubic root of 639878 is about 86.1719113985.

The spelling of 639878 in words is "six hundred thirty-nine thousand, eight hundred seventy-eight".