21111122121 has 16 divisors (see below), whose sum is σ = 29806867584. Its totient is φ = 13244891904.

The previous prime is 21111122119. The next prime is 21111122161. The reversal of 21111122121 is 12122111112.

It is a happy number.

It is not a de Polignac number, because 21111122121 - 2¹ = 21111122119 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21111122121.

It is not an unprimeable number, because it can be changed into a prime (21111122161) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1005891 + ... + 1026663.

It is an arithmetic number, because the mean of its divisors is an integer number (1862929224).

Almost surely, 2^21111122121 is an apocalyptic number.

It is an amenable number.

21111122121 is a deficient number, since it is larger than the sum of its proper divisors (8695745463).

21111122121 is a wasteful number, since it uses less digits than its factorization.

21111122121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40720.

The product of its digits is 16, while the sum is 15.

Adding to 21111122121 its reverse (12122111112), we get a palindrome (33233233233).

The spelling of 21111122121 in words is "twenty-one billion, one hundred eleven million, one hundred twenty-two thousand, one hundred twenty-one".