21111121111211 has 4 divisors (see below), whose sum is σ = 21126407949024. Its totient is φ = 21095834273400.

The previous prime is 21111121111187. The next prime is 21111121111243. The reversal of 21111121111211 is 11211112111112.

It is a happy number.

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 21111121111211 - 2⁶ = 21111121111147 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21111121111211.

It is not an unprimeable number, because it can be changed into a prime (21111121111261) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7643416835 + ... + 7643419596.

It is an arithmetic number, because the mean of its divisors is an integer number (5281601987256).

Almost surely, 2^{21111121111211} is an apocalyptic number.

21111121111211 is a deficient number, since it is larger than the sum of its proper divisors (15286837813).

21111121111211 is a wasteful number, since it uses less digits than its factorization.

21111121111211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15286837812.

The product of its digits is 8, while the sum is 17.

Adding to 21111121111211 its reverse (11211112111112), we get a palindrome (32322233222323).

Subtracting from 21111121111211 its reverse (11211112111112), we obtain a palindrome (9900009000099).

The spelling of 21111121111211 in words is "twenty-one trillion, one hundred eleven billion, one hundred twenty-one million, one hundred eleven thousand, two hundred eleven".