639538931 has 2 divisors, whose sum is σ = 639538932. Its totient is φ = 639538930.

The previous prime is 639538883. The next prime is 639538973. The reversal of 639538931 is 139835936.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 639538931 - 2¹⁰ = 639537907 is a prime.

It is a super-2 number, since 2×639538931² = 818020088529245522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (639538231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319769465 + 319769466.

It is an arithmetic number, because the mean of its divisors is an integer number (319769466).

Almost surely, 2^639538931 is an apocalyptic number.

639538931 is a deficient number, since it is larger than the sum of its proper divisors (1).

639538931 is an equidigital number, since it uses as much as digits as its factorization.

639538931 is an odious number, because the sum of its binary digits is odd.

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

The square root of 639538931 is about 25289.1069632757. The cubic root of 639538931 is about 861.5668798284.

The spelling of 639538931 in words is "six hundred thirty-nine million, five hundred thirty-eight thousand, nine hundred thirty-one".