8517659721 has 4 divisors (see below), whose sum is σ = 11356879632. Its totient is φ = 5678439812.

The previous prime is 8517659699. The next prime is 8517659729. The reversal of 8517659721 is 1279567158.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 8517659721 - 2¹³ = 8517651529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (8517659729) 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, 1419609951 + ... + 1419609956.

It is an arithmetic number, because the mean of its divisors is an integer number (2839219908).

Almost surely, 2^8517659721 is an apocalyptic number.

It is an amenable number.

8517659721 is a deficient number, since it is larger than the sum of its proper divisors (2839219911).

8517659721 is a wasteful number, since it uses less digits than its factorization.

8517659721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2839219910.

The product of its digits is 1058400, while the sum is 51.

The square root of 8517659721 is about 92291.1681635897. The cubic root of 8517659721 is about 2042.2399240782.

The spelling of 8517659721 in words is "eight billion, five hundred seventeen million, six hundred fifty-nine thousand, seven hundred twenty-one".