8666512807721 has 4 divisors (see below), whose sum is σ = 8681532761172. Its totient is φ = 8651492854272.

The previous prime is 8666512807691. The next prime is 8666512807753. The reversal of 8666512807721 is 1277082156668.

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 4274390851600 + 4392121956121 = 2067460^2 + 2095739^2 .

It is a cyclic number.

It is not a de Polignac number, because 8666512807721 - 2¹⁴ = 8666512791337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8666512807781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7509975860 + ... + 7509977013.

It is an arithmetic number, because the mean of its divisors is an integer number (2170383190293).

Almost surely, 2^{8666512807721} is an apocalyptic number.

It is an amenable number.

8666512807721 is a deficient number, since it is larger than the sum of its proper divisors (15019953451).

8666512807721 is a wasteful number, since it uses less digits than its factorization.

8666512807721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15019953450.

The product of its (nonzero) digits is 13547520, while the sum is 59.

The spelling of 8666512807721 in words is "eight trillion, six hundred sixty-six billion, five hundred twelve million, eight hundred seven thousand, seven hundred twenty-one".