81138144 has 96 divisors (see below), whose sum is σ = 228614400. Its totient is φ = 25106432.

The previous prime is 81138133. The next prime is 81138149. The reversal of 81138144 is 44183118.

It is a tau number, because it is divible by the number of its divisors (96).

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 (81138149) 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 15 ways as a sum of consecutive naturals, for example, 135157 + ... + 135755.

It is an arithmetic number, because the mean of its divisors is an integer number (2381400).

Almost surely, 2^81138144 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 81138144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (114307200).

81138144 is an abundant number, since it is smaller than the sum of its proper divisors (147476256).

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

81138144 is a wasteful number, since it uses less digits than its factorization.

81138144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 712 (or 704 counting only the distinct ones).

The product of its digits is 3072, while the sum is 30.

The square root of 81138144 is about 9007.6713972036. The cubic root of 81138144 is about 432.9207043838.

The spelling of 81138144 in words is "eighty-one million, one hundred thirty-eight thousand, one hundred forty-four".