639887 has 4 divisors (see below), whose sum is σ = 655536. Its totient is φ = 624240.

The previous prime is 639857. The next prime is 639907. The reversal of 639887 is 788936.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 639887 - 2⁸ = 639631 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41), and also a Moran number because the ratio is a prime number: 15607 = 639887 / (6 + 3 + 9 + 8 + 8 + 7).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639857) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 7763 + ... + 7844.

It is an arithmetic number, because the mean of its divisors is an integer number (163884).

2⁶³⁹⁸⁸⁷ is an apocalyptic number.

639887 is a deficient number, since it is larger than the sum of its proper divisors (15649).

639887 is a wasteful number, since it uses less digits than its factorization.

639887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15648.

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

The square root of 639887 is about 799.9293718823. The cubic root of 639887 is about 86.1723154044.

It can be divided in two parts, 6 and 39887, that added together give a palindrome (39893).

The spelling of 639887 in words is "six hundred thirty-nine thousand, eight hundred eighty-seven".