21222216 has 32 divisors (see below), whose sum is σ = 58951200. Its totient is φ = 7074000.

The previous prime is 21222211. The next prime is 21222251. The reversal of 21222216 is 61222212.

It is a Harshad number since it is a multiple of its sum of digits (18).

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

It is not an unprimeable number, because it can be changed into a prime (21222211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48910 + ... + 49341.

It is an arithmetic number, because the mean of its divisors is an integer number (1842225).

Almost surely, 2^21222216 is an apocalyptic number.

It is an amenable number.

21222216 is an abundant number, since it is smaller than the sum of its proper divisors (37728984).

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

21222216 is a wasteful number, since it uses less digits than its factorization.

21222216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98266 (or 98256 counting only the distinct ones).

The product of its digits is 192, while the sum is 18.

The square root of 21222216 is about 4606.7576450254. The cubic root of 21222216 is about 276.8621434309.

Adding to 21222216 its reverse (61222212), we get a palindrome (82444428).

The spelling of 21222216 in words is "twenty-one million, two hundred twenty-two thousand, two hundred sixteen".