638790791 has 2 divisors, whose sum is σ = 638790792. Its totient is φ = 638790790.

The previous prime is 638790787. The next prime is 638790809. The reversal of 638790791 is 197097836.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 638790791 - 2² = 638790787 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638790721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319395395 + 319395396.

It is an arithmetic number, because the mean of its divisors is an integer number (319395396).

Almost surely, 2^638790791 is an apocalyptic number.

638790791 is a deficient number, since it is larger than the sum of its proper divisors (1).

638790791 is an equidigital number, since it uses as much as digits as its factorization.

638790791 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 571536, while the sum is 50.

The square root of 638790791 is about 25274.3108907048. The cubic root of 638790791 is about 861.2307917913.

The spelling of 638790791 in words is "six hundred thirty-eight million, seven hundred ninety thousand, seven hundred ninety-one".