81231131 has 4 divisors (see below), whose sum is σ = 81268200. Its totient is φ = 81194064.

The previous prime is 81231121. The next prime is 81231133. The reversal of 81231131 is 13113218.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13113218 = 2 ⋅6556609.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81231131 is a prime.

It is a super-2 number, since 2×81231131² = 13196993287078322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81231133) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15026 + ... + 19703.

It is an arithmetic number, because the mean of its divisors is an integer number (20317050).

Almost surely, 2^81231131 is an apocalyptic number.

81231131 is a deficient number, since it is larger than the sum of its proper divisors (37069).

81231131 is a wasteful number, since it uses less digits than its factorization.

81231131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37068.

The product of its digits is 144, while the sum is 20.

The square root of 81231131 is about 9012.8314640850. The cubic root of 81231131 is about 433.0860217348.

Adding to 81231131 its reverse (13113218), we get a palindrome (94344349).

The spelling of 81231131 in words is "eighty-one million, two hundred thirty-one thousand, one hundred thirty-one".