21111112121 has 8 divisors (see below), whose sum is σ = 23220638688. Its totient is φ = 19191918900.

The previous prime is 21111112111. The next prime is 21111112157. The reversal of 21111112121 is 12121111112.

It is a de Polignac number, because none of the positive numbers 2^k-21111112121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21111112096 and 21111112105.

It is not an unprimeable number, because it can be changed into a prime (21111112111) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7929215 + ... + 7931876.

It is an arithmetic number, because the mean of its divisors is an integer number (2902579836).

Almost surely, 2^21111112121 is an apocalyptic number.

It is an amenable number.

21111112121 is a deficient number, since it is larger than the sum of its proper divisors (2109526567).

21111112121 is an equidigital number, since it uses as much as digits as its factorization.

21111112121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15861124 (or 15861102 counting only the distinct ones).

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

Adding to 21111112121 its reverse (12121111112), we get a palindrome (33232223233).

It can be divided in two parts, 21111112 and 121, that multiplied together give a palindrome (2554444552).

The spelling of 21111112121 in words is "twenty-one billion, one hundred eleven million, one hundred twelve thousand, one hundred twenty-one".