1221220222121 has 4 divisors (see below), whose sum is σ = 1221521836500. Its totient is φ = 1220918607744.

The previous prime is 1221220222111. The next prime is 1221220222151. The reversal of 1221220222121 is 1212220221221.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 110702598400 + 1110517623721 = 332720^2 + 1053811^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221220222121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1221220222093 and 1221220222102.

It is not an unprimeable number, because it can be changed into a prime (1221220222111) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 150801116 + ... + 150809213.

It is an arithmetic number, because the mean of its divisors is an integer number (305380459125).

Almost surely, 2^{1221220222121} is an apocalyptic number.

It is an amenable number.

1221220222121 is a deficient number, since it is larger than the sum of its proper divisors (301614379).

1221220222121 is an equidigital number, since it uses as much as digits as its factorization.

1221220222121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 301614378.

The product of its (nonzero) digits is 256, while the sum is 20.

Adding to 1221220222121 its reverse (1212220221221), we get a palindrome (2433440443342).

The spelling of 1221220222121 in words is "one trillion, two hundred twenty-one billion, two hundred twenty million, two hundred twenty-two thousand, one hundred twenty-one".