81318816 has 120 divisors (see below), whose sum is σ = 241954020. Its totient is φ = 26790912.

The previous prime is 81318781. The next prime is 81318817. The reversal of 81318816 is 61881318.

It can be written as a sum of positive squares in 2 ways, for example, as 74028816 + 7290000 = 8604^2 + 2700^2 .

It is a super-2 number, since 2×81318816² = 13225499671283712, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

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

It is not an unprimeable number, because it can be changed into a prime (81318817) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 354990 + ... + 355218.

Almost surely, 2^81318816 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 81318816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (120977010).

81318816 is an abundant number, since it is smaller than the sum of its proper divisors (160635204).

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

81318816 is a wasteful number, since it uses less digits than its factorization.

81318816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388 (or 371 counting only the distinct ones).

The product of its digits is 9216, while the sum is 36.

The square root of 81318816 is about 9017.6946056074. The cubic root of 81318816 is about 433.2417973651.

The spelling of 81318816 in words is "eighty-one million, three hundred eighteen thousand, eight hundred sixteen".