81131544 has 80 divisors (see below), whose sum is σ = 244749120. Its totient is φ = 24960960.

The previous prime is 81131509. The next prime is 81131551. The reversal of 81131544 is 44513118.

It is a happy number.

81131544 is a `hidden beast` number, since 8 + 113 + 1 + 544 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 3609 + ... + 13239.

It is an arithmetic number, because the mean of its divisors is an integer number (3059364).

Almost surely, 2^81131544 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 81131544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (122374560).

81131544 is an abundant number, since it is smaller than the sum of its proper divisors (163617576).

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

81131544 is a wasteful number, since it uses less digits than its factorization.

81131544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9662 (or 9649 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 81131544 is about 9007.3050353588. The cubic root of 81131544 is about 432.9089657449.

The spelling of 81131544 in words is "eighty-one million, one hundred thirty-one thousand, five hundred forty-four".