8591665981 has 2 divisors, whose sum is σ = 8591665982. Its totient is φ = 8591665980.

The previous prime is 8591665949. The next prime is 8591665987. The reversal of 8591665981 is 1895661958.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5950733881 + 2640932100 = 77141^2 + 51390^2 .

It is a cyclic number.

It is not a de Polignac number, because 8591665981 - 2⁵ = 8591665949 is a prime.

It is a super-2 number, since 2×8591665981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8591665987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4295832990 + 4295832991.

It is an arithmetic number, because the mean of its divisors is an integer number (4295832991).

Almost surely, 2^8591665981 is an apocalyptic number.

It is an amenable number.

8591665981 is a deficient number, since it is larger than the sum of its proper divisors (1).

8591665981 is an equidigital number, since it uses as much as digits as its factorization.

8591665981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4665600, while the sum is 58.

The square root of 8591665981 is about 92691.2400445695. The cubic root of 8591665981 is about 2048.1375891913.

The spelling of 8591665981 in words is "eight billion, five hundred ninety-one million, six hundred sixty-five thousand, nine hundred eighty-one".