639975 has 48 divisors (see below), whose sum is σ = 1285632. Its totient is φ = 274560.

The previous prime is 639959. The next prime is 639983. The reversal of 639975 is 579936.

It is not a de Polignac number, because 639975 - 2⁴ = 639959 is a prime.

It is a nialpdrome in base 15.

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 639975.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 12049 + ... + 12101.

It is an arithmetic number, because the mean of its divisors is an integer number (26784).

2⁶³⁹⁹⁷⁵ is an apocalyptic number.

639975 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639975 is a wasteful number, since it uses less digits than its factorization.

639975 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96 (or 91 counting only the distinct ones).

The product of its digits is 51030, while the sum is 39.

The square root of 639975 is about 799.9843748474. The cubic root of 639975 is about 86.1762654853.

Subtracting from 639975 its sum of digits (39), we obtain a palindrome (639936).

The spelling of 639975 in words is "six hundred thirty-nine thousand, nine hundred seventy-five".