81511815 has 32 divisors (see below), whose sum is σ = 162602496. Its totient is φ = 33874560.

The previous prime is 81511757. The next prime is 81511819. The reversal of 81511815 is 51811518.

It is not a de Polignac number, because 81511815 - 2⁷ = 81511687 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81511819) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 34132 + ... + 36441.

It is an arithmetic number, because the mean of its divisors is an integer number (5081328).

Almost surely, 2^81511815 is an apocalyptic number.

81511815 is a deficient number, since it is larger than the sum of its proper divisors (81090681).

81511815 is a wasteful number, since it uses less digits than its factorization.

81511815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70599.

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

The square root of 81511815 is about 9028.3893912480. The cubic root of 81511815 is about 433.5842731294.

The spelling of 81511815 in words is "eighty-one million, five hundred eleven thousand, eight hundred fifteen".