81312 has 72 divisors (see below), whose sum is σ = 268128. Its totient is φ = 21120.

The previous prime is 81307. The next prime is 81331. The reversal of 81312 is 21318.

It is a happy number.

It is a super-2 number, since 2×81312² = 13223282688, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits and also a Zuckerman number because it is divisible by the product of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 81291 and 81300.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7387 + ... + 7397.

It is an arithmetic number, because the mean of its divisors is an integer number (3724).

2⁸¹³¹² is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (134064).

81312 is an abundant number, since it is smaller than the sum of its proper divisors (186816).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81312 is a wasteful number, since it uses less digits than its factorization.

81312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42 (or 23 counting only the distinct ones).

The product of its digits is 48, while the sum is 15.

The square root of 81312 is about 285.1525907299. The cubic root of 81312 is about 43.3229692505.

It can be divided in two parts, 81 and 312, that added together give a palindrome (393).

The spelling of 81312 in words is "eighty-one thousand, three hundred twelve".