666375921 has 12 divisors (see below), whose sum is σ = 964655172. Its totient is φ = 443275776.

The previous prime is 666375887. The next prime is 666375937. The reversal of 666375921 is 129573666.

It can be written as a sum of positive squares in 2 ways, for example, as 367258896 + 299117025 = 19164^2 + 17295^2 .

It is not a de Polignac number, because 666375921 - 2⁷ = 666375793 is a prime.

It is not an unprimeable number, because it can be changed into a prime (666375421) 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, 76896 + ... + 85121.

It is an arithmetic number, because the mean of its divisors is an integer number (80387931).

Almost surely, 2^666375921 is an apocalyptic number.

It is an amenable number.

666375921 is a deficient number, since it is larger than the sum of its proper divisors (298279251).

666375921 is a wasteful number, since it uses less digits than its factorization.

666375921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162480 (or 162477 counting only the distinct ones).

The product of its digits is 408240, while the sum is 45.

The square root of 666375921 is about 25814.2580950916. The cubic root of 666375921 is about 873.4534514029.

The spelling of 666375921 in words is "six hundred sixty-six million, three hundred seventy-five thousand, nine hundred twenty-one".