639605 has 4 divisors (see below), whose sum is σ = 767532. Its totient is φ = 511680.

The previous prime is 639601. The next prime is 639631. The reversal of 639605 is 506936.

639605 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 can be written as a sum of positive squares in 2 ways, for example, as 323761 + 315844 = 569^2 + 562^2 .

It is not a de Polignac number, because 639605 - 2² = 639601 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639605.

It is not an unprimeable number, because it can be changed into a prime (639601) 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, 63956 + ... + 63965.

It is an arithmetic number, because the mean of its divisors is an integer number (191883).

2⁶³⁹⁶⁰⁵ is an apocalyptic number.

It is an amenable number.

639605 is a deficient number, since it is larger than the sum of its proper divisors (127927).

639605 is a wasteful number, since it uses less digits than its factorization.

639605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127926.

The product of its (nonzero) digits is 4860, while the sum is 29.

The square root of 639605 is about 799.7530868962. The cubic root of 639605 is about 86.1596547505.

The spelling of 639605 in words is "six hundred thirty-nine thousand, six hundred five".