It is a happy number.
It is a weak prime.
It is a cyclic number.
It is a self number, because there is not a number n which added to its sum of digits gives 121220111221831.
It is a congruent number.
Almost surely, 2121220111221831 is an apocalyptic number.
121220111221831 is an equidigital number, since it uses as much as digits as its factorization.
121220111221831 is an odious number, because the sum of its binary digits is odd.
Adding to 121220111221831 its reverse (138122111022121), we get a palindrome (259342222243952).
The spelling of 121220111221831 in words is "one hundred twenty-one trillion, two hundred twenty billion, one hundred eleven million, two hundred twenty-one thousand, eight hundred thirty-one".