639786391 has 2 divisors, whose sum is σ = 639786392. Its totient is φ = 639786390.

The previous prime is 639786341. The next prime is 639786529. The reversal of 639786391 is 193687936.

639786391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 639786391 - 2¹³ = 639778199 is a prime.

It is a super-2 number, since 2×639786391² = 818653252217609762, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639786341) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319893195 + 319893196.

It is an arithmetic number, because the mean of its divisors is an integer number (319893196).

Almost surely, 2^639786391 is an apocalyptic number.

639786391 is a deficient number, since it is larger than the sum of its proper divisors (1).

639786391 is an equidigital number, since it uses as much as digits as its factorization.

639786391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1469664, while the sum is 52.

The square root of 639786391 is about 25293.9991104610. Note that the first 3 decimals coincide. The cubic root of 639786391 is about 861.6779889608.

The spelling of 639786391 in words is "six hundred thirty-nine million, seven hundred eighty-six thousand, three hundred ninety-one".