638390521 has 2 divisors, whose sum is σ = 638390522. Its totient is φ = 638390520.

The previous prime is 638390497. The next prime is 638390537. The reversal of 638390521 is 125093836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 371525625 + 266864896 = 19275^2 + 16336^2 .

It is a cyclic number.

It is not a de Polignac number, because 638390521 - 2⁷ = 638390393 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (638390581) 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, 319195260 + 319195261.

It is an arithmetic number, because the mean of its divisors is an integer number (319195261).

Almost surely, 2^638390521 is an apocalyptic number.

It is an amenable number.

638390521 is a deficient number, since it is larger than the sum of its proper divisors (1).

638390521 is an equidigital number, since it uses as much as digits as its factorization.

638390521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 38880, while the sum is 37.

The square root of 638390521 is about 25266.3911352611. The cubic root of 638390521 is about 861.0508701429.

The spelling of 638390521 in words is "six hundred thirty-eight million, three hundred ninety thousand, five hundred twenty-one".