21111121111 has 4 divisors (see below), whose sum is σ = 21116844424. Its totient is φ = 21105397800.

The previous prime is 21111121093. The next prime is 21111121127. The reversal of 21111121111 is 11112111112.

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 21111121111 - 2²⁷ = 20976903383 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21111121091 and 21111121100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111121151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2856120 + ... + 2863501.

It is an arithmetic number, because the mean of its divisors is an integer number (5279211106).

Almost surely, 2^21111121111 is an apocalyptic number.

21111121111 is a deficient number, since it is larger than the sum of its proper divisors (5723313).

21111121111 is an equidigital number, since it uses as much as digits as its factorization.

21111121111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5723312.

The product of its digits is 4, while the sum is 13.

Adding to 21111121111 its reverse (11112111112), we get a palindrome (32223232223).

Subtracting from 21111121111 its reverse (11112111112), we obtain a palindrome (9999009999).

It can be divided in two parts, 2111112 and 1111, that multiplied together give a palindrome (2345445432).

The spelling of 21111121111 in words is "twenty-one billion, one hundred eleven million, one hundred twenty-one thousand, one hundred eleven".