81815895 has 24 divisors (see below), whose sum is σ = 162074016. Its totient is φ = 37401408.

The previous prime is 81815893. The next prime is 81815897. The reversal of 81815895 is 59851818.

It is an interprime number because it is at equal distance from previous prime (81815893) and next prime (81815897).

It is not a de Polignac number, because 81815895 - 2¹ = 81815893 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 81815895.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81815891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 129552 + ... + 130181.

It is an arithmetic number, because the mean of its divisors is an integer number (6753084).

Almost surely, 2^81815895 is an apocalyptic number.

81815895 is a deficient number, since it is larger than the sum of its proper divisors (80258121).

81815895 is a wasteful number, since it uses less digits than its factorization.

81815895 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 259751 (or 259748 counting only the distinct ones).

The product of its digits is 115200, while the sum is 45.

The square root of 81815895 is about 9045.2139278184. The cubic root of 81815895 is about 434.1227664191.

The spelling of 81815895 in words is "eighty-one million, eight hundred fifteen thousand, eight hundred ninety-five".