21222012221 has 2 divisors, whose sum is σ = 21222012222. Its totient is φ = 21222012220.

The previous prime is 21222012197. The next prime is 21222012223. The reversal of 21222012221 is 12221022212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16376320900 + 4845691321 = 127970^2 + 69611^2 .

It is a cyclic number.

It is not a de Polignac number, because 21222012221 - 2²² = 21217817917 is a prime.

It is a Sophie Germain prime.

Together with 21222012223, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21222012221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21222012223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10611006110 + 10611006111.

It is an arithmetic number, because the mean of its divisors is an integer number (10611006111).

Almost surely, 2^21222012221 is an apocalyptic number.

It is an amenable number.

21222012221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21222012221 is an equidigital number, since it uses as much as digits as its factorization.

21222012221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21222012221 its reverse (12221022212), we get a palindrome (33443034433).

Subtracting from 21222012221 its reverse (12221022212), we obtain a palindrome (9000990009).

The spelling of 21222012221 in words is "twenty-one billion, two hundred twenty-two million, twelve thousand, two hundred twenty-one".