639655 has 4 divisors (see below), whose sum is σ = 767592. Its totient is φ = 511720.

The previous prime is 639647. The next prime is 639671. The reversal of 639655 is 556936.

639655 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 639655 - 2³ = 639647 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 639655.

It is a congruent number.

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, 63961 + ... + 63970.

It is an arithmetic number, because the mean of its divisors is an integer number (191898).

2⁶³⁹⁶⁵⁵ is an apocalyptic number.

639655 is a deficient number, since it is larger than the sum of its proper divisors (127937).

639655 is a wasteful number, since it uses less digits than its factorization.

639655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127936.

The product of its digits is 24300, while the sum is 34.

The square root of 639655 is about 799.7843459333. The cubic root of 639655 is about 86.1618998186.

The spelling of 639655 in words is "six hundred thirty-nine thousand, six hundred fifty-five".