21222 has 20 divisors (see below), whose sum is σ = 47916. Its totient is φ = 7020.

The previous prime is 21221. The next prime is 21227. The reversal of 21222 is 22212.

21222 is an esthetic number in base 13, because in such base its adjacent digits differ by 1.

It is a Harshad number since it is a multiple of its sum of digits (9).

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

It is a nialpdrome in base 9 and base 13.

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 polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 97 + ... + 227.

2²¹²²² is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21222, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23958).

21222 is an abundant number, since it is smaller than the sum of its proper divisors (26694).

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

21222 is a wasteful number, since it uses less digits than its factorization.

21222 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145 (or 136 counting only the distinct ones).

The product of its digits is 16, while the sum is 9.

The square root of 21222 is about 145.6777265061. The cubic root of 21222 is about 27.6861204126.

Adding to 21222 its reverse (22212), we get a palindrome (43434).

Subtracting 21222 from its reverse (22212), we obtain a triangular number (990 = T₄₄).

It can be divided in two parts, 212 and 22, that multiplied together give a palindrome (4664).

The spelling of 21222 in words is "twenty-one thousand, two hundred twenty-two", and thus it is an iban number.