81840144 has 60 divisors (see below), whose sum is σ = 223180656. Its totient is φ = 25838784.

The previous prime is 81840133. The next prime is 81840149. The reversal of 81840144 is 44104818.

It is not an unprimeable number, because it can be changed into a prime (81840149) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14967 + ... + 19689.

Almost surely, 2^81840144 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 81840144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (111590328).

81840144 is an abundant number, since it is smaller than the sum of its proper divisors (141340512).

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

81840144 is a wasteful number, since it uses less digits than its factorization.

81840144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4772 (or 4747 counting only the distinct ones).

The product of its (nonzero) digits is 4096, while the sum is 30.

The square root of 81840144 is about 9046.5542611538. The cubic root of 81840144 is about 434.1656513342.

The spelling of 81840144 in words is "eighty-one million, eight hundred forty thousand, one hundred forty-four".