21944 has 16 divisors (see below), whose sum is σ = 44520. Its totient is φ = 10080.

The previous prime is 21943. The next prime is 21961. The reversal of 21944 is 44912.

It is a plaindrome in base 15.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21944.

It is not an unprimeable number, because it can be changed into a prime (21943) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2 + ... + 209.

2²¹⁹⁴⁴ 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 21944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22260).

21944 is an abundant number, since it is smaller than the sum of its proper divisors (22576).

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

21944 is a wasteful number, since it uses less digits than its factorization.

21944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 230 (or 226 counting only the distinct ones).

The product of its digits is 288, while the sum is 20.

The square root of 21944 is about 148.1350734971. The cubic root of 21944 is about 27.9965982262.

The spelling of 21944 in words is "twenty-one thousand, nine hundred forty-four".