81444564 has 144 divisors (see below), whose sum is σ = 234823680. Its totient is φ = 23664960.

The previous prime is 81444553. The next prime is 81444589. The reversal of 81444564 is 46544418.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 487609 + ... + 487775.

It is an arithmetic number, because the mean of its divisors is an integer number (1630720).

Almost surely, 2^81444564 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 81444564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117411840).

81444564 is an abundant number, since it is smaller than the sum of its proper divisors (153379116).

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

81444564 is a wasteful number, since it uses less digits than its factorization.

81444564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 250 (or 245 counting only the distinct ones).

The product of its digits is 61440, while the sum is 36.

The square root of 81444564 is about 9024.6642042793. The cubic root of 81444564 is about 433.4649979921.

The spelling of 81444564 in words is "eighty-one million, four hundred forty-four thousand, five hundred sixty-four".