Adding to 21221112001212 its reverse (21210021112212), we get a palindrome (42431133113424).
21221112001212 is a `hidden beast` number, since 21 + 221 + 11 + 200 + 1 + 212 = 666.
It is a congruent number.
It is an unprimeable number.
Almost surely, 221221112001212 is an apocalyptic number.
It is an amenable number.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21221112001212 is a wasteful number, since it uses less digits than its factorization.
21221112001212 is an evil number, because the sum of its binary digits is even.
The spelling of 21221112001212 in words is "twenty-one trillion, two hundred twenty-one billion, one hundred twelve million, one thousand, two hundred twelve".