21011011111 has 2 divisors, whose sum is σ = 21011011112. Its totient is φ = 21011011110.

The previous prime is 21011011079. The next prime is 21011011139. The reversal of 21011011111 is 11111011012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21011011111 - 2⁵ = 21011011079 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011011711) 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 as a sum of consecutive naturals, namely, 10505505555 + 10505505556.

It is an arithmetic number, because the mean of its divisors is an integer number (10505505556).

Almost surely, 2^21011011111 is an apocalyptic number.

21011011111 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011011111 is an equidigital number, since it uses as much as digits as its factorization.

21011011111 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2, while the sum is 10.

Adding to 21011011111 its reverse (11111011012), we get a palindrome (32122022123).

Subtracting from 21011011111 its reverse (11111011012), we obtain a palindrome (9900000099).

The spelling of 21011011111 in words is "twenty-one billion, eleven million, eleven thousand, one hundred eleven".