81319865 has 24 divisors (see below), whose sum is σ = 108144960. Its totient is φ = 58655520.

The previous prime is 81319859. The next prime is 81319919. The reversal of 81319865 is 56891318.

It is not a de Polignac number, because 81319865 - 2¹² = 81315769 is a prime.

It is a super-2 number, since 2×81319865² = 13225840887236450, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 83612 + ... + 84578.

It is an arithmetic number, because the mean of its divisors is an integer number (4506040).

Almost surely, 2^81319865 is an apocalyptic number.

It is an amenable number.

81319865 is a deficient number, since it is larger than the sum of its proper divisors (26825095).

81319865 is a wasteful number, since it uses less digits than its factorization.

81319865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1133 (or 1122 counting only the distinct ones).

The product of its digits is 51840, while the sum is 41.

The square root of 81319865 is about 9017.7527688444. The cubic root of 81319865 is about 433.2436602742.

The spelling of 81319865 in words is "eighty-one million, three hundred nineteen thousand, eight hundred sixty-five".