639705 has 16 divisors (see below), whose sum is σ = 1116864. Its totient is φ = 310080.

The previous prime is 639703. The next prime is 639713. The reversal of 639705 is 507936.

639705 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 639705 - 2¹ = 639703 is a prime.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (639701) 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, 1774 + ... + 2103.

It is an arithmetic number, because the mean of its divisors is an integer number (69804).

2⁶³⁹⁷⁰⁵ is an apocalyptic number.

It is an amenable number.

639705 is a deficient number, since it is larger than the sum of its proper divisors (477159).

639705 is a wasteful number, since it uses less digits than its factorization.

639705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3896.

The product of its (nonzero) digits is 5670, while the sum is 30.

The square root of 639705 is about 799.8156037488. The cubic root of 639705 is about 86.1641447698.

Subtracting from 639705 its reverse (507936), we obtain a square (131769 = 363²).

The spelling of 639705 in words is "six hundred thirty-nine thousand, seven hundred five".