21844 has 12 divisors (see below), whose sum is σ = 39424. Its totient is φ = 10584.

The previous prime is 21841. The next prime is 21851. The reversal of 21844 is 44812.

21844 is nontrivially palindromic in base 3.

It is a hoax number, since the sum of its digits (19) coincides with the sum of the digits of its distinct prime factors.

It is a nialpdrome in base 4 and base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 109 + ... + 235.

21844 is a Friedman number, since it can be written as (4^8-4)/(2+1), using all its digits and the basic arithmetic operations.

2²¹⁸⁴⁴ is an apocalyptic number.

It is an amenable number.

21844 is a deficient number, since it is larger than the sum of its proper divisors (17580).

21844 is a wasteful number, since it uses less digits than its factorization.

21844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 174 (or 172 counting only the distinct ones).

The product of its digits is 256, while the sum is 19.

The square root of 21844 is about 147.7971582947. The cubic root of 21844 is about 27.9540061227.

It can be divided in two parts, 218 and 44, that added together give a palindrome (262).

The spelling of 21844 in words is "twenty-one thousand, eight hundred forty-four".