639835957 has 4 divisors (see below), whose sum is σ = 653449536. Its totient is φ = 626222380.

The previous prime is 639835921. The next prime is 639835991. The reversal of 639835957 is 759538936.

It is a happy number.

639835957 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, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639835957 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639835898 and 639835907.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639835057) 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, 6806719 + ... + 6806812.

It is an arithmetic number, because the mean of its divisors is an integer number (163362384).

Almost surely, 2^639835957 is an apocalyptic number.

It is an amenable number.

639835957 is a deficient number, since it is larger than the sum of its proper divisors (13613579).

639835957 is a wasteful number, since it uses less digits than its factorization.

639835957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13613578.

The product of its digits is 6123600, while the sum is 55.

The square root of 639835957 is about 25294.9788890997. The cubic root of 639835957 is about 861.7002405690.

The spelling of 639835957 in words is "six hundred thirty-nine million, eight hundred thirty-five thousand, nine hundred fifty-seven".