21121111211 has 4 divisors (see below), whose sum is σ = 21160152624. Its totient is φ = 21082069800.

The previous prime is 21121111153. The next prime is 21121111279. The reversal of 21121111211 is 11211112112.

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 21121111211 - 2¹⁸ = 21120849067 is a prime.

It is a super-2 number, since 2×21121111211² (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 (21121111411) 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 3 ways as a sum of consecutive naturals, for example, 19519895 + ... + 19520976.

It is an arithmetic number, because the mean of its divisors is an integer number (5290038156).

Almost surely, 2^21121111211 is an apocalyptic number.

21121111211 is a deficient number, since it is larger than the sum of its proper divisors (39041413).

21121111211 is an equidigital number, since it uses as much as digits as its factorization.

21121111211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39041412.

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

Adding to 21121111211 its reverse (11211112112), we get a palindrome (32332223323).

Subtracting from 21121111211 its reverse (11211112112), we obtain a palindrome (9909999099).

It can be divided in two parts, 2 and 1121111211, that multiplied together give a palindrome (2242222422).

The spelling of 21121111211 in words is "twenty-one billion, one hundred twenty-one million, one hundred eleven thousand, two hundred eleven".