639526021 has 2 divisors, whose sum is σ = 639526022. Its totient is φ = 639526020.

The previous prime is 639526007. The next prime is 639526049. The reversal of 639526021 is 120625936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 545222500 + 94303521 = 23350^2 + 9711^2 .

It is a cyclic number.

It is not a de Polignac number, because 639526021 - 2¹⁷ = 639394949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639526061) 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, 319763010 + 319763011.

It is an arithmetic number, because the mean of its divisors is an integer number (319763011).

Almost surely, 2^639526021 is an apocalyptic number.

It is an amenable number.

639526021 is a deficient number, since it is larger than the sum of its proper divisors (1).

639526021 is an equidigital number, since it uses as much as digits as its factorization.

639526021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 19440, while the sum is 34.

The square root of 639526021 is about 25288.8517137493. The cubic root of 639526021 is about 861.5610824730.

The spelling of 639526021 in words is "six hundred thirty-nine million, five hundred twenty-six thousand, twenty-one".