666920661 has 24 divisors (see below), whose sum is σ = 980135520. Its totient is φ = 403069920.

The previous prime is 666920599. The next prime is 666920707. The reversal of 666920661 is 166029666.

666920661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 666920661 - 2¹⁹ = 666396373 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666920161) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 138846 + ... + 143568.

It is an arithmetic number, because the mean of its divisors is an integer number (40838980).

Almost surely, 2^666920661 is an apocalyptic number.

It is an amenable number.

666920661 is a deficient number, since it is larger than the sum of its proper divisors (313214859).

666920661 is a wasteful number, since it uses less digits than its factorization.

666920661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5137 (or 5126 counting only the distinct ones).

The product of its (nonzero) digits is 139968, while the sum is 42.

The square root of 666920661 is about 25824.8070854363. The cubic root of 666920661 is about 873.6913928938.

The spelling of 666920661 in words is "six hundred sixty-six million, nine hundred twenty thousand, six hundred sixty-one".