11111221221 has 16 divisors (see below), whose sum is σ = 15342716928. Its totient is φ = 7145161200.

The previous prime is 11111221217. The next prime is 11111221229. The reversal of 11111221221 is 12212211111.

It is a happy number.

It is not a de Polignac number, because 11111221221 - 2² = 11111221217 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 11111221221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11111221229) 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 15 ways as a sum of consecutive naturals, for example, 166035 + ... + 223136.

It is an arithmetic number, because the mean of its divisors is an integer number (958919808).

Almost surely, 2^11111221221 is an apocalyptic number.

It is an amenable number.

11111221221 is a deficient number, since it is larger than the sum of its proper divisors (4231495707).

11111221221 is a wasteful number, since it uses less digits than its factorization.

11111221221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 389512.

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

Adding to 11111221221 its reverse (12212211111), we get a palindrome (23323432332).

It can be divided in two parts, 1111 and 1221221, that multiplied together give a palindrome (1356776531).

The spelling of 11111221221 in words is "eleven billion, one hundred eleven million, two hundred twenty-one thousand, two hundred twenty-one".