21324 has 12 divisors (see below), whose sum is σ = 49784. Its totient is φ = 7104.

The previous prime is 21323. The next prime is 21341. The reversal of 21324 is 42312.

21324 is nontrivially palindromic in base 9.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Harshad number since it is a multiple of its sum of digits (12), and also a Moran number because the ratio is a prime number: 1777 = 21324 / (2 + 1 + 3 + 2 + 4).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21323) 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, 877 + ... + 900.

2²¹³²⁴ is an apocalyptic number.

It is an amenable number.

21324 is an abundant number, since it is smaller than the sum of its proper divisors (28460).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24892).

21324 is a wasteful number, since it uses less digits than its factorization.

21324 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1784 (or 1782 counting only the distinct ones).

The product of its digits is 48, while the sum is 12.

The square root of 21324 is about 146.0273946902. The cubic root of 21324 is about 27.7304057766.

Subtracting from 21324 its sum of digits (12), we obtain a palindrome (21312).

Adding to 21324 its reverse (42312), we get a palindrome (63636).

It can be divided in two parts, 2 and 1324, that added together give a triangular number (1326 = T₅₁).

The spelling of 21324 in words is "twenty-one thousand, three hundred twenty-four", and thus it is an iban number.