639125521 has 2 divisors, whose sum is σ = 639125522. Its totient is φ = 639125520.

The previous prime is 639125503. The next prime is 639125579. The reversal of 639125521 is 125521936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 521619921 + 117505600 = 22839^2 + 10840^2 .

It is a cyclic number.

It is not a de Polignac number, because 639125521 - 2⁷ = 639125393 is a prime.

It is not a weakly prime, because it can be changed into another prime (639125321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319562760 + 319562761.

It is an arithmetic number, because the mean of its divisors is an integer number (319562761).

Almost surely, 2^639125521 is an apocalyptic number.

It is an amenable number.

639125521 is a deficient number, since it is larger than the sum of its proper divisors (1).

639125521 is an equidigital number, since it uses as much as digits as its factorization.

639125521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16200, while the sum is 34.

The square root of 639125521 is about 25280.9319646250. The cubic root of 639125521 is about 861.3811954645.

The spelling of 639125521 in words is "six hundred thirty-nine million, one hundred twenty-five thousand, five hundred twenty-one".