668520616961 has 2 divisors, whose sum is σ = 668520616962. Its totient is φ = 668520616960.

The previous prime is 668520616949. The next prime is 668520617041. The reversal of 668520616961 is 169616025866.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 538967412736 + 129553204225 = 734144^2 + 359935^2 .

It is a cyclic number.

It is not a de Polignac number, because 668520616961 - 2²⁶ = 668453508097 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 668520616897 and 668520616906.

It is not a weakly prime, because it can be changed into another prime (668520616061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334260308480 + 334260308481.

It is an arithmetic number, because the mean of its divisors is an integer number (334260308481).

Almost surely, 2^668520616961 is an apocalyptic number.

It is an amenable number.

668520616961 is a deficient number, since it is larger than the sum of its proper divisors (1).

668520616961 is an equidigital number, since it uses as much as digits as its factorization.

668520616961 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5598720, while the sum is 56.

The spelling of 668520616961 in words is "six hundred sixty-eight billion, five hundred twenty million, six hundred sixteen thousand, nine hundred sixty-one".