Adding to 21213612324604 its reverse (40642321631212), we get a palindrome (61855933955816).
It is a congruent number.
Almost surely, 221213612324604 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.
21213612324604 is a wasteful number, since it uses less digits than its factorization.
21213612324604 is an odious number, because the sum of its binary digits is odd.
The spelling of 21213612324604 in words is "twenty-one trillion, two hundred thirteen billion, six hundred twelve million, three hundred twenty-four thousand, six hundred four".