1221100111221 has 16 divisors (see below), whose sum is σ = 1631770445760. Its totient is φ = 812249976960.

The previous prime is 1221100111123. The next prime is 1221100111229. The reversal of 1221100111221 is 1221110011221.

It is a happy number.

It is not a de Polignac number, because 1221100111221 - 2²⁷ = 1220965893493 is a prime.

It is a super-2 number, since 2×1221100111221² (a number of 25 digits) contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1221100111221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221100111229) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2643135 + ... + 3070563.

It is an arithmetic number, because the mean of its divisors is an integer number (101985652860).

Almost surely, 2^{1221100111221} is an apocalyptic number.

It is an amenable number.

1221100111221 is a deficient number, since it is larger than the sum of its proper divisors (410670334539).

1221100111221 is a wasteful number, since it uses less digits than its factorization.

1221100111221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 429556.

The product of its (nonzero) digits is 16, while the sum is 15.

Adding to 1221100111221 its reverse (1221110011221), we get a palindrome (2442210122442).

The spelling of 1221100111221 in words is "one trillion, two hundred twenty-one billion, one hundred million, one hundred eleven thousand, two hundred twenty-one".