21212221111 has 4 divisors (see below), whose sum is σ = 21612451752. Its totient is φ = 20811990472.

The previous prime is 21212221061. The next prime is 21212221117. The reversal of 21212221111 is 11112221212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21212221111 - 2¹⁹ = 21211696823 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212221117) 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 3 ways as a sum of consecutive naturals, for example, 200115241 + ... + 200115346.

It is an arithmetic number, because the mean of its divisors is an integer number (5403112938).

Almost surely, 2^21212221111 is an apocalyptic number.

21212221111 is a deficient number, since it is larger than the sum of its proper divisors (400230641).

21212221111 is an equidigital number, since it uses as much as digits as its factorization.

21212221111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 400230640.

The product of its digits is 32, while the sum is 16.

Adding to 21212221111 its reverse (11112221212), we get a palindrome (32324442323).

The spelling of 21212221111 in words is "twenty-one billion, two hundred twelve million, two hundred twenty-one thousand, one hundred eleven".