1221221111221 has 4 divisors (see below), whose sum is σ = 1221243057792. Its totient is φ = 1221199164652.

The previous prime is 1221221111207. The next prime is 1221221111239. The reversal of 1221221111221 is 1221111221221.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1221221111221 - 2⁷ = 1221221111093 is a prime.

It is a super-2 number, since 2×1221221111221² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221221111261) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10889605 + ... + 11001178.

It is an arithmetic number, because the mean of its divisors is an integer number (305310764448).

Almost surely, 2^{1221221111221} is an apocalyptic number.

It is an amenable number.

1221221111221 is a deficient number, since it is larger than the sum of its proper divisors (21946571).

1221221111221 is an equidigital number, since it uses as much as digits as its factorization.

1221221111221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21946570.

The product of its digits is 64, while the sum is 19.

Adding to 1221221111221 its reverse (1221111221221), we get a palindrome (2442332332442).

The spelling of 1221221111221 in words is "one trillion, two hundred twenty-one billion, two hundred twenty-one million, one hundred eleven thousand, two hundred twenty-one".