81115731131 has 4 divisors (see below), whose sum is σ = 81152553912. Its totient is φ = 81078908352.

The previous prime is 81115731119. The next prime is 81115731143. The reversal of 81115731131 is 13113751118.

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

It is an interprime number because it is at equal distance from previous prime (81115731119) and next prime (81115731143).

It is a cyclic number.

It is not a de Polignac number, because 81115731131 - 2²² = 81111536827 is a prime.

It is a super-2 number, since 2×81115731131² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81115733131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18408086 + ... + 18412491.

It is an arithmetic number, because the mean of its divisors is an integer number (20288138478).

Almost surely, 2^81115731131 is an apocalyptic number.

81115731131 is a deficient number, since it is larger than the sum of its proper divisors (36822781).

81115731131 is a wasteful number, since it uses less digits than its factorization.

81115731131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36822780.

The product of its digits is 2520, while the sum is 32.

The spelling of 81115731131 in words is "eighty-one billion, one hundred fifteen million, seven hundred thirty-one thousand, one hundred thirty-one".