638839813 has 2 divisors, whose sum is σ = 638839814. Its totient is φ = 638839812.

The previous prime is 638839807. The next prime is 638839867. The reversal of 638839813 is 318938836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 483912004 + 154927809 = 21998^2 + 12447^2 .

It is a cyclic number.

It is not a de Polignac number, because 638839813 - 2⁵ = 638839781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638839013) 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, 319419906 + 319419907.

It is an arithmetic number, because the mean of its divisors is an integer number (319419907).

Almost surely, 2^638839813 is an apocalyptic number.

It is an amenable number.

638839813 is a deficient number, since it is larger than the sum of its proper divisors (1).

638839813 is an equidigital number, since it uses as much as digits as its factorization.

638839813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 746496, while the sum is 49.

The square root of 638839813 is about 25275.2806710430. The cubic root of 638839813 is about 861.2528220483.

The spelling of 638839813 in words is "six hundred thirty-eight million, eight hundred thirty-nine thousand, eight hundred thirteen".