1221222222221 has 2 divisors, whose sum is σ = 1221222222222. Its totient is φ = 1221222222220.

The previous prime is 1221222222007. The next prime is 1221222222251. The reversal of 1221222222221 is 1222222221221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 995465152900 + 225757069321 = 997730^2 + 475139^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221222222221 - 2¹⁴ = 1221222205837 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221222222251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610611111110 + 610611111111.

It is an arithmetic number, because the mean of its divisors is an integer number (610611111111).

Almost surely, 2^{1221222222221} is an apocalyptic number.

It is an amenable number.

1221222222221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221222222221 is an equidigital number, since it uses as much as digits as its factorization.

1221222222221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1024, while the sum is 23.

Adding to 1221222222221 its reverse (1222222221221), we get a palindrome (2443444443442).

The spelling of 1221222222221 in words is "one trillion, two hundred twenty-one billion, two hundred twenty-two million, two hundred twenty-two thousand, two hundred twenty-one".