21222112221221 has 2 divisors, whose sum is σ = 21222112221222. Its totient is φ = 21222112221220.

The previous prime is 21222112221209. The next prime is 21222112221229. The reversal of 21222112221221 is 12212221122212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16606554112996 + 4615558108225 = 4075114^2 + 2148385^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21222112221221 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21222112221229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10611056110610 + 10611056110611.

It is an arithmetic number, because the mean of its divisors is an integer number (10611056110611).

Almost surely, 2^{21222112221221} is an apocalyptic number.

It is an amenable number.

21222112221221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21222112221221 is an equidigital number, since it uses as much as digits as its factorization.

21222112221221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 512, while the sum is 23.

Adding to 21222112221221 its reverse (12212221122212), we get a palindrome (33434333343433).

The spelling of 21222112221221 in words is "twenty-one trillion, two hundred twenty-two billion, one hundred twelve million, two hundred twenty-one thousand, two hundred twenty-one".