666363681 has 12 divisors (see below), whose sum is σ = 965954340. Its totient is φ = 442659840.

The previous prime is 666363623. The next prime is 666363727. The reversal of 666363681 is 186363666.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 522579600 + 143784081 = 22860^2 + 11991^2 .

It is not a de Polignac number, because 666363681 - 2⁷ = 666363553 is a prime.

It is a super-2 number, since 2×666363681² = 888081110711739522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (666363601) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 129216 + ... + 134273.

It is an arithmetic number, because the mean of its divisors is an integer number (80496195).

Almost surely, 2^666363681 is an apocalyptic number.

It is an amenable number.

666363681 is a deficient number, since it is larger than the sum of its proper divisors (299590659).

666363681 is a wasteful number, since it uses less digits than its factorization.

666363681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 263776 (or 263773 counting only the distinct ones).

The product of its digits is 559872, while the sum is 45.

The square root of 666363681 is about 25814.0210157193. The cubic root of 666363681 is about 873.4481035027.

The spelling of 666363681 in words is "six hundred sixty-six million, three hundred sixty-three thousand, six hundred eighty-one".