18444 has 24 divisors (see below), whose sum is σ = 45360. Its totient is φ = 5824.

The previous prime is 18443. The next prime is 18451. The reversal of 18444 is 44481.

It is a super-2 number, since 2×18444² = 680362272, which contains 22 as substring.

It is an Ulam number.

It is a nialpdrome in base 12.

It is a self number, because there is not a number n which added to its sum of digits gives 18444.

It is not an unprimeable number, because it can be changed into a prime (18443) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 322 + ... + 374.

It is an arithmetic number, because the mean of its divisors is an integer number (1890).

2¹⁸⁴⁴⁴ 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 18444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22680).

18444 is an abundant number, since it is smaller than the sum of its proper divisors (26916).

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

18444 is a wasteful number, since it uses less digits than its factorization.

18444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89 (or 87 counting only the distinct ones).

The product of its digits is 512, while the sum is 21.

The square root of 18444 is about 135.8086889709. The cubic root of 18444 is about 26.4211492602.

The spelling of 18444 in words is "eighteen thousand, four hundred forty-four".