21211111211 has 4 divisors (see below), whose sum is σ = 21213954024. Its totient is φ = 21208268400.

The previous prime is 21211111147. The next prime is 21211111253. The reversal of 21211111211 is 11211111212.

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 21211111211 - 2⁶ = 21211111147 is a prime.

It is a super-2 number, since 2×21211111211² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21211110211) 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, 1410185 + ... + 1425146.

It is an arithmetic number, because the mean of its divisors is an integer number (5303488506).

Almost surely, 2^21211111211 is an apocalyptic number.

21211111211 is a deficient number, since it is larger than the sum of its proper divisors (2842813).

21211111211 is an equidigital number, since it uses as much as digits as its factorization.

21211111211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2842812.

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

Adding to 21211111211 its reverse (11211111212), we get a palindrome (32422222423).

Subtracting from 21211111211 its reverse (11211111212), we obtain a palindrome (9999999999).

It can be divided in two parts, 212111 and 11211, that added together give a palindrome (223322).

The spelling of 21211111211 in words is "twenty-one billion, two hundred eleven million, one hundred eleven thousand, two hundred eleven".