639979633961 has 2 divisors, whose sum is σ = 639979633962. Its totient is φ = 639979633960.

The previous prime is 639979633921. The next prime is 639979633963. The reversal of 639979633961 is 169336979936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 552049000000 + 87930633961 = 743000^2 + 296531^2 .

It is a cyclic number.

It is not a de Polignac number, because 639979633961 - 2²² = 639975439657 is a prime.

Together with 639979633963, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (639979633963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319989816980 + 319989816981.

It is an arithmetic number, because the mean of its divisors is an integer number (319989816981).

Almost surely, 2^639979633961 is an apocalyptic number.

It is an amenable number.

639979633961 is a deficient number, since it is larger than the sum of its proper divisors (1).

639979633961 is an equidigital number, since it uses as much as digits as its factorization.

639979633961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 267846264, while the sum is 71.

The spelling of 639979633961 in words is "six hundred thirty-nine billion, nine hundred seventy-nine million, six hundred thirty-three thousand, nine hundred sixty-one".