638320757 has 2 divisors, whose sum is σ = 638320758. Its totient is φ = 638320756.

The previous prime is 638320729. The next prime is 638320807. The reversal of 638320757 is 757023836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 536431921 + 101888836 = 23161^2 + 10094^2 .

It is a cyclic number.

It is not a de Polignac number, because 638320757 - 2²⁸ = 369885301 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638322757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319160378 + 319160379.

It is an arithmetic number, because the mean of its divisors is an integer number (319160379).

Almost surely, 2^638320757 is an apocalyptic number.

It is an amenable number.

638320757 is a deficient number, since it is larger than the sum of its proper divisors (1).

638320757 is an equidigital number, since it uses as much as digits as its factorization.

638320757 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 211680, while the sum is 41.

The square root of 638320757 is about 25265.0105283968. The cubic root of 638320757 is about 861.0195034798.

The spelling of 638320757 in words is "six hundred thirty-eight million, three hundred twenty thousand, seven hundred fifty-seven".