666261756015991 has 2 divisors, whose sum is σ = 666261756015992. Its totient is φ = 666261756015990.

The previous prime is 666261756015901. The next prime is 666261756016009. The reversal of 666261756015991 is 199510657162666.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 666261756015991 - 2¹⁵ = 666261755983223 is a prime.

It is a super-3 number, since 3×666261756015991³ (a number of 45 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 666261756015991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666261756015901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (31) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333130878007995 + 333130878007996.

It is an arithmetic number, because the mean of its divisors is an integer number (333130878007996).

Almost surely, 2^{666261756015991} is an apocalyptic number.

666261756015991 is a deficient number, since it is larger than the sum of its proper divisors (1).

666261756015991 is an equidigital number, since it uses as much as digits as its factorization.

666261756015991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 220449600, while the sum is 70.

The spelling of 666261756015991 in words is "six hundred sixty-six trillion, two hundred sixty-one billion, seven hundred fifty-six million, fifteen thousand, nine hundred ninety-one".