639385 has 4 divisors (see below), whose sum is σ = 767268. Its totient is φ = 511504.

The previous prime is 639371. The next prime is 639391. The reversal of 639385 is 583936.

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

It can be written as a sum of positive squares in 2 ways, for example, as 85849 + 553536 = 293^2 + 744^2 .

It is a cyclic number.

It is not a de Polignac number, because 639385 - 2⁷ = 639257 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 639385.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63934 + ... + 63943.

It is an arithmetic number, because the mean of its divisors is an integer number (191817).

2⁶³⁹³⁸⁵ is an apocalyptic number.

It is an amenable number.

639385 is a deficient number, since it is larger than the sum of its proper divisors (127883).

639385 is a wasteful number, since it uses less digits than its factorization.

639385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127882.

The product of its digits is 19440, while the sum is 34.

The square root of 639385 is about 799.6155326155. The cubic root of 639385 is about 86.1497750603.

It can be divided in two parts, 639 and 385, that added together give a 10-th power (1024 = 2¹⁰).

The spelling of 639385 in words is "six hundred thirty-nine thousand, three hundred eighty-five".