639790391 has 4 divisors (see below), whose sum is σ = 640327872. Its totient is φ = 639252912.

The previous prime is 639790381. The next prime is 639790397. The reversal of 639790391 is 193097936.

639790391 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 639790391 - 2¹⁴ = 639774007 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639790397) 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, 266951 + ... + 269336.

It is an arithmetic number, because the mean of its divisors is an integer number (160081968).

Almost surely, 2^639790391 is an apocalyptic number.

639790391 is a deficient number, since it is larger than the sum of its proper divisors (537481).

639790391 is a wasteful number, since it uses less digits than its factorization.

639790391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 537480.

The product of its (nonzero) digits is 275562, while the sum is 47.

The square root of 639790391 is about 25294.0781804754. The cubic root of 639790391 is about 861.6797847189.

The spelling of 639790391 in words is "six hundred thirty-nine million, seven hundred ninety thousand, three hundred ninety-one".