21211111111 has 4 divisors (see below), whose sum is σ = 22327485400. Its totient is φ = 20094736824.

The previous prime is 21211111091. The next prime is 21211111127. The reversal of 21211111111 is 11111111212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21211111111 - 2⁷ = 21211110983 is a prime.

It is a super-2 number, since 2×21211111111² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

21211111111 is a modest number, since divided by 111111 gives 21211 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 21211111091 and 21211111100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211118111) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 558187116 + ... + 558187153.

It is an arithmetic number, because the mean of its divisors is an integer number (5581871350).

Almost surely, 2^21211111111 is an apocalyptic number.

21211111111 is a deficient number, since it is larger than the sum of its proper divisors (1116374289).

21211111111 is a wasteful number, since it uses less digits than its factorization.

21211111111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1116374288.

The product of its digits is 4, while the sum is 13.

Adding to 21211111111 its reverse (11111111212), we get a palindrome (32322222323).

It can be divided in two parts, 212 and 11111111, that multiplied together give a palindrome (2355555532).

The spelling of 21211111111 in words is "twenty-one billion, two hundred eleven million, one hundred eleven thousand, one hundred eleven".