639824 has 10 divisors (see below), whose sum is σ = 1239690. Its totient is φ = 319904.

The previous prime is 639757. The next prime is 639833. The reversal of 639824 is 428936.

It can be written as a sum of positive squares in only one way, i.e., 446224 + 193600 = 668^2 + 440^2 .

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 639824.

It is an unprimeable number.

639824 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19979 + ... + 20010.

It is an arithmetic number, because the mean of its divisors is an integer number (123969).

2⁶³⁹⁸²⁴ is an apocalyptic number.

It is an amenable number.

639824 is a deficient number, since it is larger than the sum of its proper divisors (599866).

639824 is a wasteful number, since it uses less digits than its factorization.

639824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39997 (or 39991 counting only the distinct ones).

The product of its digits is 10368, while the sum is 32.

The square root of 639824 is about 799.8899924365. The cubic root of 639824 is about 86.1694872832.

The spelling of 639824 in words is "six hundred thirty-nine thousand, eight hundred twenty-four".