21224 has 16 divisors (see below), whose sum is σ = 45600. Its totient is φ = 9072.

The previous prime is 21221. The next prime is 21227. The reversal of 21224 is 42212.

21224 is an esthetic number in base 13, because in such base its adjacent digits differ by 1.

It is an interprime number because it is at equal distance from previous prime (21221) and next prime (21227).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221) 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, 134 + ... + 245.

It is an arithmetic number, because the mean of its divisors is an integer number (2850).

2²¹²²⁴ is an apocalyptic number.

It is an amenable number.

21224 is an abundant number, since it is smaller than the sum of its proper divisors (24376).

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 (22800).

21224 is a wasteful number, since it uses less digits than its factorization.

21224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 392 (or 388 counting only the distinct ones).

The product of its digits is 32, while the sum is 11.

The square root of 21224 is about 145.6845908118. The cubic root of 21224 is about 27.6869901154.

Adding to 21224 its reverse (42212), we get a palindrome (63436).

The spelling of 21224 in words is "twenty-one thousand, two hundred twenty-four", and thus it is an iban number.