81131859233 has 4 divisors (see below), whose sum is σ = 81134327700. Its totient is φ = 81129390768.

The previous prime is 81131859229. The next prime is 81131859239. The reversal of 81131859233 is 33295813118.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 48368325184 + 32763534049 = 219928^2 + 181007^2 .

It is a cyclic number.

It is not a de Polignac number, because 81131859233 - 2² = 81131859229 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81131859239) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1184258 + ... + 1250891.

It is an arithmetic number, because the mean of its divisors is an integer number (20283581925).

Almost surely, 2^81131859233 is an apocalyptic number.

It is an amenable number.

81131859233 is a deficient number, since it is larger than the sum of its proper divisors (2468467).

81131859233 is a wasteful number, since it uses less digits than its factorization.

81131859233 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2468466.

The product of its digits is 155520, while the sum is 44.

The spelling of 81131859233 in words is "eighty-one billion, one hundred thirty-one million, eight hundred fifty-nine thousand, two hundred thirty-three".