6664164721 has 4 divisors (see below), whose sum is σ = 6789903732. Its totient is φ = 6538425712.

The previous prime is 6664164701. The next prime is 6664164737. The reversal of 6664164721 is 1274614666.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2847396321 + 3816768400 = 53361^2 + 61780^2 .

It is a cyclic number.

It is not a de Polignac number, because 6664164721 - 2⁷ = 6664164593 is a prime.

It is a super-2 number, since 2×6664164721² = 88822182857242015682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6664164701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 62869426 + ... + 62869531.

It is an arithmetic number, because the mean of its divisors is an integer number (1697475933).

Almost surely, 2^6664164721 is an apocalyptic number.

It is an amenable number.

6664164721 is a deficient number, since it is larger than the sum of its proper divisors (125739011).

6664164721 is a wasteful number, since it uses less digits than its factorization.

6664164721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125739010.

The product of its digits is 290304, while the sum is 43.

The square root of 6664164721 is about 81634.3354294013. The cubic root of 6664164721 is about 1881.8365862013.

The spelling of 6664164721 in words is "six billion, six hundred sixty-four million, one hundred sixty-four thousand, seven hundred twenty-one".