21101220111 has 4 divisors (see below), whose sum is σ = 28134960152. Its totient is φ = 14067480072.

The previous prime is 21101220109. The next prime is 21101220163. The reversal of 21101220111 is 11102210112.

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

It is not a de Polignac number, because 21101220111 - 2¹ = 21101220109 is a prime.

It is a super-2 number, since 2×21101220111² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21101220181) 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, 3516870016 + ... + 3516870021.

It is an arithmetic number, because the mean of its divisors is an integer number (7033740038).

Almost surely, 2^21101220111 is an apocalyptic number.

21101220111 is a deficient number, since it is larger than the sum of its proper divisors (7033740041).

21101220111 is an equidigital number, since it uses as much as digits as its factorization.

21101220111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7033740040.

The product of its (nonzero) digits is 8, while the sum is 12.

Adding to 21101220111 its reverse (11102210112), we get a palindrome (32203430223).

Subtracting from 21101220111 its reverse (11102210112), we obtain a palindrome (9999009999).

It can be divided in two parts, 2110 and 1220111, that added together give a palindrome (1222221).

The spelling of 21101220111 in words is "twenty-one billion, one hundred one million, two hundred twenty thousand, one hundred eleven".