81685331 has 16 divisors (see below), whose sum is σ = 101170944. Its totient is φ = 64221984.

The previous prime is 81685309. The next prime is 81685333. The reversal of 81685331 is 13358618.

It is a cyclic number.

It is not a de Polignac number, because 81685331 - 2⁶ = 81685267 is a prime.

It is a super-2 number, since 2×81685331² = 13344986601159122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81685291 and 81685300.

It is not an unprimeable number, because it can be changed into a prime (81685333) 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, 12080 + ... + 17586.

It is an arithmetic number, because the mean of its divisors is an integer number (6323184).

Almost surely, 2^81685331 is an apocalyptic number.

81685331 is a deficient number, since it is larger than the sum of its proper divisors (19485613).

81685331 is a wasteful number, since it uses less digits than its factorization.

81685331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5690.

The product of its digits is 17280, while the sum is 35.

The square root of 81685331 is about 9037.9937486148. The cubic root of 81685331 is about 433.8917152175.

The spelling of 81685331 in words is "eighty-one million, six hundred eighty-five thousand, three hundred thirty-one".