639842 has 12 divisors (see below), whose sum is σ = 1116630. Its totient is φ = 274176.

The previous prime is 639839. The next prime is 639851. The reversal of 639842 is 248936.

It can be written as a sum of positive squares in only one way, i.e., 625681 + 14161 = 791^2 + 119^2 .

It is a junction number, because it is equal to n+sod(n) for n = 639799 and 639808.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3167 + ... + 3362.

2⁶³⁹⁸⁴² is an apocalyptic number.

639842 is a deficient number, since it is larger than the sum of its proper divisors (476788).

639842 is a wasteful number, since it uses less digits than its factorization.

639842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6545 (or 6538 counting only the distinct ones).

The product of its digits is 10368, while the sum is 32.

The square root of 639842 is about 799.9012439045. The cubic root of 639842 is about 86.1702953368.

The spelling of 639842 in words is "six hundred thirty-nine thousand, eight hundred forty-two".