639844 has 12 divisors (see below), whose sum is σ = 1178800. Its totient is φ = 303048.

The previous prime is 639839. The next prime is 639851. The reversal of 639844 is 448936.

It is a hoax number, since the sum of its digits (34) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

639844 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 3 ways as a sum of consecutive naturals, for example, 4134 + ... + 4285.

2⁶³⁹⁸⁴⁴ is an apocalyptic number.

It is an amenable number.

639844 is a deficient number, since it is larger than the sum of its proper divisors (538956).

639844 is a wasteful number, since it uses less digits than its factorization.

639844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8442 (or 8440 counting only the distinct ones).

The product of its digits is 20736, while the sum is 34.

The square root of 639844 is about 799.9024940579. The cubic root of 639844 is about 86.1703851196.

The spelling of 639844 in words is "six hundred thirty-nine thousand, eight hundred forty-four".