666368721 has 32 divisors (see below), whose sum is σ = 1021680000. Its totient is φ = 428972544.

The previous prime is 666368711. The next prime is 666368723. The reversal of 666368721 is 127863666.

It is not a de Polignac number, because 666368721 - 2⁶ = 666368657 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (666368723) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 100105 + ... + 106553.

It is an arithmetic number, because the mean of its divisors is an integer number (31927500).

Almost surely, 2^666368721 is an apocalyptic number.

It is an amenable number.

666368721 is a deficient number, since it is larger than the sum of its proper divisors (355311279).

666368721 is a wasteful number, since it uses less digits than its factorization.

666368721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6590 (or 6584 counting only the distinct ones).

The product of its digits is 435456, while the sum is 45.

The square root of 666368721 is about 25814.1186369010. The cubic root of 666368721 is about 873.4503055872.

It can be divided in two parts, 66636 and 8721, that added together give a palindrome (75357).

The spelling of 666368721 in words is "six hundred sixty-six million, three hundred sixty-eight thousand, seven hundred twenty-one".