668888888888809 has 2 divisors, whose sum is σ = 668888888888810. Its totient is φ = 668888888888808.

The previous prime is 668888888888761. The next prime is 668888888888813. The reversal of 668888888888809 is 908888888888866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 546318305143209 + 122570583745600 = 23373453^2 + 11071160^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-668888888888809 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 668888888888696 and 668888888888705.

It is not a weakly prime, because it can be changed into another prime (668888888888839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334444444444404 + 334444444444405.

It is an arithmetic number, because the mean of its divisors is an integer number (334444444444405).

Almost surely, 2^{668888888888809} is an apocalyptic number.

It is an amenable number.

668888888888809 is a deficient number, since it is larger than the sum of its proper divisors (1).

668888888888809 is an equidigital number, since it uses as much as digits as its factorization.

668888888888809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2783138807808, while the sum is 109.

The spelling of 668888888888809 in words is "six hundred sixty-eight trillion, eight hundred eighty-eight billion, eight hundred eighty-eight million, eight hundred eighty-eight thousand, eight hundred nine".