Almost surely, 221221201212100 is an apocalyptic number.
21221201212100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.
It is an amenable number.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21221201212100 is a wasteful number, since it uses less digits than its factorization.
21221201212100 is an odious number, because the sum of its binary digits is odd.
Adding to 21221201212100 its reverse (121210212212), we get a palindrome (21342411424312).
The spelling of 21221201212100 in words is "twenty-one trillion, two hundred twenty-one billion, two hundred one million, two hundred twelve thousand, one hundred".