81993024 has 84 divisors (see below), whose sum is σ = 236317536. Its totient is φ = 27180288.

The previous prime is 81993017. The next prime is 81993029. The reversal of 81993024 is 42039918.

It is a Cunningham number, because it is equal to 9055²-1.

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

It is a self number, because there is not a number n which added to its sum of digits gives 81993024.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81993029) 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 11 ways as a sum of consecutive naturals, for example, 162757 + ... + 163259.

It is an arithmetic number, because the mean of its divisors is an integer number (2813304).

Almost surely, 2^81993024 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 81993024, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118158768).

81993024 is an abundant number, since it is smaller than the sum of its proper divisors (154324512).

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

81993024 is a wasteful number, since it uses less digits than its factorization.

81993024 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 804 (or 791 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 81993024 is about 9054.9999447819. Note that the first 4 decimals coincide. The cubic root of 81993024 is about 434.4358282670.

The spelling of 81993024 in words is "eighty-one million, nine hundred ninety-three thousand, twenty-four".