639939 has 16 divisors (see below), whose sum is σ = 915200. Its totient is φ = 396576.

The previous prime is 639937. The next prime is 639941. The reversal of 639939 is 939936.

639939 = 22² + 23² + ... + 124².

639939 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (639937) and next prime (639941).

It is not a de Polignac number, because 639939 - 2¹ = 639937 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639897 and 639906.

It is not an unprimeable number, because it can be changed into a prime (639937) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5817 + ... + 5925.

It is an arithmetic number, because the mean of its divisors is an integer number (57200).

2⁶³⁹⁹³⁹ is an apocalyptic number.

639939 is a deficient number, since it is larger than the sum of its proper divisors (275261).

639939 is a wasteful number, since it uses less digits than its factorization.

639939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 234.

The product of its digits is 39366, while the sum is 39.

The square root of 639939 is about 799.9618740915. The cubic root of 639939 is about 86.1746495869.

The spelling of 639939 in words is "six hundred thirty-nine thousand, nine hundred thirty-nine".