21222217 has 4 divisors (see below), whose sum is σ = 21301380. Its totient is φ = 21143056.

The previous prime is 21222211. The next prime is 21222251. The reversal of 21222217 is 71222212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4280761 + 16941456 = 2069^2 + 4116^2 .

It is a cyclic number.

It is not a de Polignac number, because 21222217 - 2¹⁵ = 21189449 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21222194 and 21222203.

It is not an unprimeable number, because it can be changed into a prime (21222211) 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, 39178 + ... + 39715.

It is an arithmetic number, because the mean of its divisors is an integer number (5325345).

Almost surely, 2^21222217 is an apocalyptic number.

It is an amenable number.

21222217 is a deficient number, since it is larger than the sum of its proper divisors (79163).

21222217 is an equidigital number, since it uses as much as digits as its factorization.

21222217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79162.

The product of its digits is 224, while the sum is 19.

The square root of 21222217 is about 4606.7577535616. The cubic root of 21222217 is about 276.8621477796.

Adding to 21222217 its reverse (71222212), we get a palindrome (92444429).

The spelling of 21222217 in words is "twenty-one million, two hundred twenty-two thousand, two hundred seventeen".