21011111111 has 16 divisors (see below), whose sum is σ = 21429878400. Its totient is φ = 20596824288.

The previous prime is 21011111101. The next prime is 21011111119. The reversal of 21011111111 is 11111111012.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21011111111 - 2³⁴ = 3831241927 is a prime.

It is a super-3 number, since 3×21011111111³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

21011111111 is a modest number, since divided by 111111 gives 21011 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 21011111092 and 21011111101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011111119) 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 in 15 ways as a sum of consecutive naturals, for example, 8274080 + ... + 8276618.

It is an arithmetic number, because the mean of its divisors is an integer number (1339367400).

Almost surely, 2^21011111111 is an apocalyptic number.

21011111111 is a deficient number, since it is larger than the sum of its proper divisors (418767289).

21011111111 is a wasteful number, since it uses less digits than its factorization.

21011111111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3358.

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

Adding to 21011111111 its reverse (11111111012), we get a palindrome (32122222123).

Subtracting from 21011111111 its reverse (11111111012), we obtain a palindrome (9900000099).

The spelling of 21011111111 in words is "twenty-one billion, eleven million, one hundred eleven thousand, one hundred eleven".