21211211111 has 2 divisors, whose sum is σ = 21211211112. Its totient is φ = 21211211110.

The previous prime is 21211211071. The next prime is 21211211123. The reversal of 21211211111 is 11111211212.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21211211111 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21211211171) 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, 10605605555 + 10605605556.

It is an arithmetic number, because the mean of its divisors is an integer number (10605605556).

Almost surely, 2^21211211111 is an apocalyptic number.

21211211111 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211211111 is an equidigital number, since it uses as much as digits as its factorization.

21211211111 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8, while the sum is 14.

Adding to 21211211111 its reverse (11111211212), we get a palindrome (32322422323).

The spelling of 21211211111 in words is "twenty-one billion, two hundred eleven million, two hundred eleven thousand, one hundred eleven".