639399 has 4 divisors (see below), whose sum is σ = 852536. Its totient is φ = 426264.

The previous prime is 639391. The next prime is 639433. The reversal of 639399 is 993936.

639399 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 639399 - 2³ = 639391 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639391) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106564 + ... + 106569.

It is an arithmetic number, because the mean of its divisors is an integer number (213134).

2⁶³⁹³⁹⁹ is an apocalyptic number.

639399 is a deficient number, since it is larger than the sum of its proper divisors (213137).

639399 is a wasteful number, since it uses less digits than its factorization.

639399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213136.

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

The square root of 639399 is about 799.6242867747. The cubic root of 639399 is about 86.1504038353.

The spelling of 639399 in words is "six hundred thirty-nine thousand, three hundred ninety-nine".