11111212221 has 16 divisors (see below), whose sum is σ = 15740025600. Its totient is φ = 6958744128.

The previous prime is 11111212213. The next prime is 11111212247. The reversal of 11111212221 is 12221211111.

It is a happy number.

It is not a de Polignac number, because 11111212221 - 2³ = 11111212213 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 11111212221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11111212201) 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, 1722661 + ... + 1729098.

It is an arithmetic number, because the mean of its divisors is an integer number (983751600).

Almost surely, 2^11111212221 is an apocalyptic number.

It is an amenable number.

11111212221 is a deficient number, since it is larger than the sum of its proper divisors (4628813379).

11111212221 is a wasteful number, since it uses less digits than its factorization.

11111212221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3451828.

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

Adding to 11111212221 its reverse (12221211111), we get a palindrome (23332423332).

The spelling of 11111212221 in words is "eleven billion, one hundred eleven million, two hundred twelve thousand, two hundred twenty-one".