639839 has 2 divisors, whose sum is σ = 639840. Its totient is φ = 639838.

The previous prime is 639833. The next prime is 639851. The reversal of 639839 is 938936.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639839 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639833) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319919 + 319920.

It is an arithmetic number, because the mean of its divisors is an integer number (319920).

2⁶³⁹⁸³⁹ is an apocalyptic number.

639839 is a deficient number, since it is larger than the sum of its proper divisors (1).

639839 is an equidigital number, since it uses as much as digits as its factorization.

639839 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34992, while the sum is 38.

The square root of 639839 is about 799.8993686708. The cubic root of 639839 is about 86.1701606622.

The spelling of 639839 in words is "six hundred thirty-nine thousand, eight hundred thirty-nine".