638974813 has 2 divisors, whose sum is σ = 638974814. Its totient is φ = 638974812.

The previous prime is 638974781. The next prime is 638974841. The reversal of 638974813 is 318479836.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 376437604 + 262537209 = 19402^2 + 16203^2 .

It is a cyclic number.

It is not a de Polignac number, because 638974813 - 2⁵ = 638974781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638972813) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319487406 + 319487407.

It is an arithmetic number, because the mean of its divisors is an integer number (319487407).

Almost surely, 2^638974813 is an apocalyptic number.

It is an amenable number.

638974813 is a deficient number, since it is larger than the sum of its proper divisors (1).

638974813 is an equidigital number, since it uses as much as digits as its factorization.

638974813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 870912, while the sum is 49.

The square root of 638974813 is about 25277.9511234594. The cubic root of 638974813 is about 861.3134845908.

The spelling of 638974813 in words is "six hundred thirty-eight million, nine hundred seventy-four thousand, eight hundred thirteen".