81531155 has 4 divisors (see below), whose sum is σ = 97837392. Its totient is φ = 65224920.

The previous prime is 81531143. The next prime is 81531169. The reversal of 81531155 is 55113518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 55113518 = 2 ⋅27556759.

It is not a de Polignac number, because 81531155 - 2²⁰ = 80482579 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8153111 + ... + 8153120.

It is an arithmetic number, because the mean of its divisors is an integer number (24459348).

Almost surely, 2^81531155 is an apocalyptic number.

81531155 is a deficient number, since it is larger than the sum of its proper divisors (16306237).

81531155 is a wasteful number, since it uses less digits than its factorization.

81531155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16306236.

The product of its digits is 3000, while the sum is 29.

The square root of 81531155 is about 9029.4603936226. The cubic root of 81531155 is about 433.6185620512.

The spelling of 81531155 in words is "eighty-one million, five hundred thirty-one thousand, one hundred fifty-five".