Adding to 21222211222221 its reverse (12222211222212), we get a palindrome (33444422444433).
Subtracting from 21222211222221 its reverse (12222211222212), we obtain a palindrome (9000000000009).
It is a happy number.
It is a cyclic number.
It is a Curzon number.
It is a congruent number.
Almost surely, 221222211222221 is an apocalyptic number.
It is an amenable number.
21222211222221 is a wasteful number, since it uses less digits than its factorization.
21222211222221 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 1333092.
The spelling of 21222211222221 in words is "twenty-one trillion, two hundred twenty-two billion, two hundred eleven million, two hundred twenty-two thousand, two hundred twenty-one".