639976 has 8 divisors (see below), whose sum is σ = 1199970. Its totient is φ = 319984.

The previous prime is 639959. The next prime is 639983. The reversal of 639976 is 679936.

639976 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 624100 + 15876 = 790^2 + 126^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a nialpdrome in base 15.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39991 + ... + 40006.

2⁶³⁹⁹⁷⁶ is an apocalyptic number.

It is an amenable number.

639976 is a deficient number, since it is larger than the sum of its proper divisors (559994).

639976 is a wasteful number, since it uses less digits than its factorization.

639976 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80003 (or 79999 counting only the distinct ones).

The product of its digits is 61236, while the sum is 40.

The square root of 639976 is about 799.9849998594. The cubic root of 639976 is about 86.1763103705.

Subtracting from 639976 its sum of digits (40), we obtain a palindrome (639936).

The spelling of 639976 in words is "six hundred thirty-nine thousand, nine hundred seventy-six".