21222220 has 24 divisors (see below), whose sum is σ = 45604944. Its totient is φ = 8291136.

The previous prime is 21222211. The next prime is 21222251. The reversal of 21222220 is 2222212.

It is a self number, because there is not a number n which added to its sum of digits gives 21222220.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11479 + ... + 13198.

It is an arithmetic number, because the mean of its divisors is an integer number (1900206).

Almost surely, 2^21222220 is an apocalyptic number.

21222220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21222220 is an abundant number, since it is smaller than the sum of its proper divisors (24382724).

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

21222220 is a wasteful number, since it uses less digits than its factorization.

21222220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24729 (or 24727 counting only the distinct ones).

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

The square root of 21222220 is about 4606.7580791702. The cubic root of 21222220 is about 276.8621608254.

Adding to 21222220 its reverse (2222212), we get a palindrome (23444432).

The spelling of 21222220 in words is "twenty-one million, two hundred twenty-two thousand, two hundred twenty".