81591744 has 112 divisors (see below), whose sum is σ = 235577888. Its totient is φ = 24772608.

The previous prime is 81591733. The next prime is 81591779. The reversal of 81591744 is 44719518.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 241944 + ... + 242280.

It is an arithmetic number, because the mean of its divisors is an integer number (2103374).

Almost surely, 2^81591744 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 81591744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117788944).

81591744 is an abundant number, since it is smaller than the sum of its proper divisors (153986144).

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

81591744 is a wasteful number, since it uses less digits than its factorization.

81591744 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 462 (or 452 counting only the distinct ones).

The product of its digits is 40320, while the sum is 39.

The square root of 81591744 is about 9032.8148436686. The cubic root of 81591744 is about 433.7259484431.

The spelling of 81591744 in words is "eighty-one million, five hundred ninety-one thousand, seven hundred forty-four".