639915 has 16 divisors (see below), whose sum is σ = 1052448. Its totient is φ = 331776.

The previous prime is 639911. The next prime is 639937. The reversal of 639915 is 519936.

It is not a de Polignac number, because 639915 - 2² = 639911 is a prime.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (639911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22 + ... + 1131.

It is an arithmetic number, because the mean of its divisors is an integer number (65778).

2⁶³⁹⁹¹⁵ is an apocalyptic number.

639915 is a deficient number, since it is larger than the sum of its proper divisors (412533).

639915 is a wasteful number, since it uses less digits than its factorization.

639915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1198.

The product of its digits is 7290, while the sum is 33.

The square root of 639915 is about 799.9468732360. The cubic root of 639915 is about 86.1735722876.

The spelling of 639915 in words is "six hundred thirty-nine thousand, nine hundred fifteen".