81311328 has 144 divisors (see below), whose sum is σ = 269601696. Its totient is φ = 22763520.

The previous prime is 81311327. The next prime is 81311339. The reversal of 81311328 is 82311318.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×81311328² = 13223064122247168, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81311327) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 106468 + ... + 107228.

It is an arithmetic number, because the mean of its divisors is an integer number (1872234).

Almost surely, 2^81311328 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 81311328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (134800848).

81311328 is an abundant number, since it is smaller than the sum of its proper divisors (188290368).

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

81311328 is a wasteful number, since it uses less digits than its factorization.

81311328 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 837 (or 826 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 81311328 is about 9017.2794123283. The cubic root of 81311328 is about 433.2284990318.

The spelling of 81311328 in words is "eighty-one million, three hundred eleven thousand, three hundred twenty-eight".