666666686666665 has 16 divisors (see below), whose sum is σ = 800054136600768. Its totient is φ = 533297275638336.

The previous prime is 666666686666621. The next prime is 666666686666699. The reversal of 666666686666665 is 566666686666666.

It is a cyclic number.

It is not a de Polignac number, because 666666686666665 - 2⁴⁷ = 525929198311337 is a prime.

It is a super-2 number, since 2×666666686666665² (a number of 30 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 666666686666665.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9023971707 + ... + 9024045583.

It is an arithmetic number, because the mean of its divisors is an integer number (50003383537548).

Almost surely, 2^{666666686666665} is an apocalyptic number.

It is an amenable number.

666666686666665 is a deficient number, since it is larger than the sum of its proper divisors (133387449934103).

666666686666665 is a wasteful number, since it uses less digits than its factorization.

666666686666665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 171528.

The product of its digits is 522427760640, while the sum is 91.

Subtracting from 666666686666665 its reverse (566666686666666), we obtain a palindrome (99999999999999).

The spelling of 666666686666665 in words is "six hundred sixty-six trillion, six hundred sixty-six billion, six hundred eighty-six million, six hundred sixty-six thousand, six hundred sixty-five".