66668888889991 has 2 divisors, whose sum is σ = 66668888889992. Its totient is φ = 66668888889990.

The previous prime is 66668888889923. The next prime is 66668888890001. The reversal of 66668888889991 is 19998888886666.

66668888889991 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 is a cyclic number.

It is not a de Polignac number, because 66668888889991 - 2¹¹ = 66668888887943 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66668888889791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33334444444995 + 33334444444996.

It is an arithmetic number, because the mean of its divisors is an integer number (33334444444996).

Almost surely, 2^{66668888889991} is an apocalyptic number.

66668888889991 is a deficient number, since it is larger than the sum of its proper divisors (1).

66668888889991 is an equidigital number, since it uses as much as digits as its factorization.

66668888889991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 247669456896, while the sum is 100.

The spelling of 66668888889991 in words is "sixty-six trillion, six hundred sixty-eight billion, eight hundred eighty-eight million, eight hundred eighty-nine thousand, nine hundred ninety-one".