639831539 has 4 divisors (see below), whose sum is σ = 653445024. Its totient is φ = 626218056.

The previous prime is 639831487. The next prime is 639831557. The reversal of 639831539 is 935138936.

639831539 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 is a cyclic number.

It is not a de Polignac number, because 639831539 - 2¹² = 639827443 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (47), and also a Moran number because the ratio is a prime number: 13613437 = 639831539 / (6 + 3 + 9 + 8 + 3 + 1 + 5 + 3 + 9).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639831493 and 639831502.

It is not an unprimeable number, because it can be changed into a prime (639831559) 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, 6806672 + ... + 6806765.

It is an arithmetic number, because the mean of its divisors is an integer number (163361256).

Almost surely, 2^639831539 is an apocalyptic number.

639831539 is a deficient number, since it is larger than the sum of its proper divisors (13613485).

639831539 is a wasteful number, since it uses less digits than its factorization.

639831539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13613484.

The product of its digits is 524880, while the sum is 47.

The square root of 639831539 is about 25294.8915593643. The cubic root of 639831539 is about 861.6982572479.

The spelling of 639831539 in words is "six hundred thirty-nine million, eight hundred thirty-one thousand, five hundred thirty-nine".