21822 has 8 divisors (see below), whose sum is σ = 43656. Its totient is φ = 7272.

The previous prime is 21821. The next prime is 21839. The reversal of 21822 is 22812.

It is a sphenic number, since it is the product of 3 distinct primes.

21822 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821) 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, 1813 + ... + 1824.

It is an arithmetic number, because the mean of its divisors is an integer number (5457).

2²¹⁸²² is an apocalyptic number.

21822 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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 (21828).

21822 is a wasteful number, since it uses less digits than its factorization.

21822 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3642.

The product of its digits is 64, while the sum is 15.

The square root of 21822 is about 147.7227132164. The cubic root of 21822 is about 27.9446184234.

Subtracting 21822 from its reverse (22812), we obtain a triangular number (990 = T₄₄).

The spelling of 21822 in words is "twenty-one thousand, eight hundred twenty-two".