21111222121 has 4 divisors (see below), whose sum is σ = 23030424144. Its totient is φ = 19192020100.

The previous prime is 21111222113. The next prime is 21111222151. The reversal of 21111222121 is 12122211112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21111222121 - 2³ = 21111222113 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21111222095 and 21111222104.

It is not an unprimeable number, because it can be changed into a prime (21111222151) 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, 959600995 + ... + 959601016.

It is an arithmetic number, because the mean of its divisors is an integer number (5757606036).

Almost surely, 2^21111222121 is an apocalyptic number.

It is an amenable number.

21111222121 is a deficient number, since it is larger than the sum of its proper divisors (1919202023).

21111222121 is a wasteful number, since it uses less digits than its factorization.

21111222121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1919202022.

The product of its digits is 32, while the sum is 16.

Adding to 21111222121 its reverse (12122211112), we get a palindrome (33233433233).

The spelling of 21111222121 in words is "twenty-one billion, one hundred eleven million, two hundred twenty-two thousand, one hundred twenty-one".