81185511 has 16 divisors (see below), whose sum is σ = 121281408. Its totient is φ = 47872800.

The previous prime is 81185479. The next prime is 81185513. The reversal of 81185511 is 11558118.

It is not a de Polignac number, because 81185511 - 2⁵ = 81185479 is a prime.

It is a super-2 number, since 2×81185511² = 13182174392662242, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81185513) 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, 32025 + ... + 34466.

It is an arithmetic number, because the mean of its divisors is an integer number (7580088).

Almost surely, 2^81185511 is an apocalyptic number.

81185511 is a deficient number, since it is larger than the sum of its proper divisors (40095897).

81185511 is a wasteful number, since it uses less digits than its factorization.

81185511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66542.

The product of its digits is 1600, while the sum is 30.

The square root of 81185511 is about 9010.3002724660. The cubic root of 81185511 is about 433.0049317887.

The spelling of 81185511 in words is "eighty-one million, one hundred eighty-five thousand, five hundred eleven".