639974081 has 2 divisors, whose sum is σ = 639974082. Its totient is φ = 639974080.

The previous prime is 639974053. The next prime is 639974107. The reversal of 639974081 is 180479936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 613800625 + 26173456 = 24775^2 + 5116^2 .

It is a cyclic number.

It is not a de Polignac number, because 639974081 - 2¹⁸ = 639711937 is a prime.

It is a super-2 number, since 2×639974081² = 819133648703589122, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (639974021) 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, 319987040 + 319987041.

It is an arithmetic number, because the mean of its divisors is an integer number (319987041).

Almost surely, 2^639974081 is an apocalyptic number.

It is an amenable number.

639974081 is a deficient number, since it is larger than the sum of its proper divisors (1).

639974081 is an equidigital number, since it uses as much as digits as its factorization.

639974081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 326592, while the sum is 47.

The square root of 639974081 is about 25297.7090069437. The cubic root of 639974081 is about 861.7622423572.

The spelling of 639974081 in words is "six hundred thirty-nine million, nine hundred seventy-four thousand, eighty-one".