668888888888921 has 2 divisors, whose sum is σ = 668888888888922. Its totient is φ = 668888888888920.

The previous prime is 668888888888839. The next prime is 668888888888999. The reversal of 668888888888921 is 129888888888866.

668888888888921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 624139746218521 + 44749142670400 = 24982789^2 + 6689480^2 .

It is a cyclic number.

It is not a de Polignac number, because 668888888888921 - 2¹⁰ = 668888888887897 is a prime.

It is not a weakly prime, because it can be changed into another prime (668888888881921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334444444444460 + 334444444444461.

It is an arithmetic number, because the mean of its divisors is an integer number (334444444444461).

Almost surely, 2^{668888888888921} is an apocalyptic number.

It is an amenable number.

668888888888921 is a deficient number, since it is larger than the sum of its proper divisors (1).

668888888888921 is an equidigital number, since it uses as much as digits as its factorization.

668888888888921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 695784701952, while the sum is 104.

The spelling of 668888888888921 in words is "six hundred sixty-eight trillion, eight hundred eighty-eight billion, eight hundred eighty-eight million, eight hundred eighty-eight thousand, nine hundred twenty-one".