21110111111 has 2 divisors, whose sum is σ = 21110111112. Its totient is φ = 21110111110.

The previous prime is 21110111107. The next prime is 21110111149. The reversal of 21110111111 is 11111101112.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21110111111 - 2² = 21110111107 is a prime.

It is a super-2 number, since 2×21110111111² (a number of 21 digits) contains 22 as substring.

21110111111 is a modest number, since divided by 111111 gives 21110 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 21110111092 and 21110111101.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21110111411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555055555 + 10555055556.

It is an arithmetic number, because the mean of its divisors is an integer number (10555055556).

Almost surely, 2^21110111111 is an apocalyptic number.

21110111111 is a deficient number, since it is larger than the sum of its proper divisors (1).

21110111111 is an equidigital number, since it uses as much as digits as its factorization.

21110111111 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2, while the sum is 11.

Adding to 21110111111 its reverse (11111101112), we get a palindrome (32221212223).

Subtracting from 21110111111 its reverse (11111101112), we obtain a palindrome (9999009999).

The spelling of 21110111111 in words is "twenty-one billion, one hundred ten million, one hundred eleven thousand, one hundred eleven".