21222400 has 66 divisors (see below), whose sum is σ = 52669310. Its totient is φ = 8478720.

The previous prime is 21222391. The next prime is 21222401. The reversal of 21222400 is 422212.

It can be written as a sum of positive squares in 3 ways, for example, as 1721344 + 19501056 = 1312^2 + 4416^2 .

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21222401) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 25186 + ... + 26014.

Almost surely, 2^21222400 is an apocalyptic number.

21222400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21222400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26334655).

21222400 is an abundant number, since it is smaller than the sum of its proper divisors (31446910).

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

21222400 is an equidigital number, since it uses as much as digits as its factorization.

21222400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 859 (or 836 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 13.

The square root of 21222400 is about 4606.7776156442. Note that the first 3 decimals coincide. The cubic root of 21222400 is about 276.8629435749.

Adding to 21222400 its reverse (422212), we get a palindrome (21644612).

The spelling of 21222400 in words is "twenty-one million, two hundred twenty-two thousand, four hundred".