8517385721 has 16 divisors (see below), whose sum is σ = 9697934400. Its totient is φ = 7415540928.

The previous prime is 8517385699. The next prime is 8517385729. The reversal of 8517385721 is 1275837158.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 8517385721 - 2¹⁴ = 8517369337 is a prime.

It is not an unprimeable number, because it can be changed into a prime (8517385729) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19886 + ... + 132023.

It is an arithmetic number, because the mean of its divisors is an integer number (606120900).

Almost surely, 2^8517385721 is an apocalyptic number.

It is an amenable number.

8517385721 is a deficient number, since it is larger than the sum of its proper divisors (1180548679).

8517385721 is a wasteful number, since it uses less digits than its factorization.

8517385721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 152168.

The product of its digits is 470400, while the sum is 47.

The square root of 8517385721 is about 92289.6837192543. The cubic root of 8517385721 is about 2042.2180252719.

The spelling of 8517385721 in words is "eight billion, five hundred seventeen million, three hundred eighty-five thousand, seven hundred twenty-one".