81131165 has 16 divisors (see below), whose sum is σ = 99836928. Its totient is φ = 63263616.

The previous prime is 81131147. The next prime is 81131173. The reversal of 81131165 is 56113118.

It is a cyclic number.

It is not a de Polignac number, because 81131165 - 2²² = 76936861 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 73004 + ... + 74106.

It is an arithmetic number, because the mean of its divisors is an integer number (6239808).

Almost surely, 2^81131165 is an apocalyptic number.

It is an amenable number.

81131165 is a deficient number, since it is larger than the sum of its proper divisors (18705763).

81131165 is a wasteful number, since it uses less digits than its factorization.

81131165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1468.

The product of its digits is 720, while the sum is 26.

The square root of 81131165 is about 9007.2839968550. The cubic root of 81131165 is about 432.9082916431.

The spelling of 81131165 in words is "eighty-one million, one hundred thirty-one thousand, one hundred sixty-five".