81320031 has 40 divisors (see below), whose sum is σ = 135384480. Its totient is φ = 48299328.

The previous prime is 81320023. The next prime is 81320053. The reversal of 81320031 is 13002318.

It is not a de Polignac number, because 81320031 - 2³ = 81320023 is a prime.

It is a super-2 number, since 2×81320031² = 13225894883681922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81319986 and 81320013.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81320021) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 29206 + ... + 31868.

It is an arithmetic number, because the mean of its divisors is an integer number (3384612).

Almost surely, 2^81320031 is an apocalyptic number.

81320031 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

81320031 is a deficient number, since it is larger than the sum of its proper divisors (54064449).

81320031 is a wasteful number, since it uses less digits than its factorization.

81320031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2717 (or 2708 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 81320031 is about 9017.7619729066. The cubic root of 81320031 is about 433.2439550706.

Adding to 81320031 its reverse (13002318), we get a palindrome (94322349).

The spelling of 81320031 in words is "eighty-one million, three hundred twenty thousand, thirty-one".