21011211111 has 16 divisors (see below), whose sum is σ = 30566401920. Its totient is φ = 12732133920.

The previous prime is 21011211103. The next prime is 21011211187. The reversal of 21011211111 is 11111211012.

It is not a de Polignac number, because 21011211111 - 2³ = 21011211103 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011211101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 189816 + ... + 279378.

It is an arithmetic number, because the mean of its divisors is an integer number (1910400120).

Almost surely, 2^21011211111 is an apocalyptic number.

21011211111 is a deficient number, since it is larger than the sum of its proper divisors (9555190809).

21011211111 is a wasteful number, since it uses less digits than its factorization.

21011211111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96686.

The product of its (nonzero) digits is 4, while the sum is 12.

Adding to 21011211111 its reverse (11111211012), we get a palindrome (32122422123).

Subtracting from 21011211111 its reverse (11111211012), we obtain a palindrome (9900000099).

The spelling of 21011211111 in words is "twenty-one billion, eleven million, two hundred eleven thousand, one hundred eleven".