639382921 has 2 divisors, whose sum is σ = 639382922. Its totient is φ = 639382920.

The previous prime is 639382883. The next prime is 639382951. The reversal of 639382921 is 129283936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 378108025 + 261274896 = 19445^2 + 16164^2 .

It is a cyclic number.

It is not a de Polignac number, because 639382921 - 2¹¹ = 639380873 is a prime.

It is not a weakly prime, because it can be changed into another prime (639382951) 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, 319691460 + 319691461.

It is an arithmetic number, because the mean of its divisors is an integer number (319691461).

Almost surely, 2^639382921 is an apocalyptic number.

It is an amenable number.

639382921 is a deficient number, since it is larger than the sum of its proper divisors (1).

639382921 is an equidigital number, since it uses as much as digits as its factorization.

639382921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 139968, while the sum is 43.

The square root of 639382921 is about 25286.0222455016. The cubic root of 639382921 is about 861.4968168640.

The spelling of 639382921 in words is "six hundred thirty-nine million, three hundred eighty-two thousand, nine hundred twenty-one".