81931331 has 8 divisors (see below), whose sum is σ = 83223360. Its totient is φ = 80644032.

The previous prime is 81931327. The next prime is 81931349. The reversal of 81931331 is 13313918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81931331 - 2² = 81931327 is a prime.

It is a super-2 number, since 2×81931331² = 13425485998863122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81931294 and 81931303.

It is not an unprimeable number, because it can be changed into a prime (81931631) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 50966 + ... + 52548.

It is an arithmetic number, because the mean of its divisors is an integer number (10402920).

Almost surely, 2^81931331 is an apocalyptic number.

81931331 is a deficient number, since it is larger than the sum of its proper divisors (1292029).

81931331 is a wasteful number, since it uses less digits than its factorization.

81931331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2365.

The product of its digits is 1944, while the sum is 29.

The square root of 81931331 is about 9051.5927327736. The cubic root of 81931331 is about 434.3268418635.

The spelling of 81931331 in words is "eighty-one million, nine hundred thirty-one thousand, three hundred thirty-one".