666680081 has 2 divisors, whose sum is σ = 666680082. Its totient is φ = 666680080.

The previous prime is 666680071. The next prime is 666680099. The reversal of 666680081 is 180086666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 401641681 + 265038400 = 20041^2 + 16280^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-666680081 is a prime.

It is a super-2 number, since 2×666680081² = 888924660804333122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (666680071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333340040 + 333340041.

It is an arithmetic number, because the mean of its divisors is an integer number (333340041).

Almost surely, 2^666680081 is an apocalyptic number.

It is an amenable number.

666680081 is a deficient number, since it is larger than the sum of its proper divisors (1).

666680081 is an equidigital number, since it uses as much as digits as its factorization.

666680081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 82944, while the sum is 41.

The square root of 666680081 is about 25820.1487408574. The cubic root of 666680081 is about 873.5863239468.

The spelling of 666680081 in words is "six hundred sixty-six million, six hundred eighty thousand, eighty-one".