639982661 has 2 divisors, whose sum is σ = 639982662. Its totient is φ = 639982660.

The previous prime is 639982639. The next prime is 639982669. The reversal of 639982661 is 166289936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 567630625 + 72352036 = 23825^2 + 8506^2 .

It is a cyclic number.

It is not a de Polignac number, because 639982661 - 2¹⁴ = 639966277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639982669) 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, 319991330 + 319991331.

It is an arithmetic number, because the mean of its divisors is an integer number (319991331).

Almost surely, 2^639982661 is an apocalyptic number.

It is an amenable number.

639982661 is a deficient number, since it is larger than the sum of its proper divisors (1).

639982661 is an equidigital number, since it uses as much as digits as its factorization.

639982661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 839808, while the sum is 50.

The square root of 639982661 is about 25297.8785869487. The cubic root of 639982661 is about 861.7660934960.

The spelling of 639982661 in words is "six hundred thirty-nine million, nine hundred eighty-two thousand, six hundred sixty-one".