21113112121 has 4 divisors (see below), whose sum is σ = 21841150500. Its totient is φ = 20385073744.

The previous prime is 21113112019. The next prime is 21113112143. The reversal of 21113112121 is 12121131112.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 10924430400 + 10188681721 = 104520^2 + 100939^2 .

It is a cyclic number.

It is not a de Polignac number, because 21113112121 - 2²⁵ = 21079557689 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21113112095 and 21113112104.

It is not an unprimeable number, because it can be changed into a prime (21113112421) 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, 364019146 + ... + 364019203.

It is an arithmetic number, because the mean of its divisors is an integer number (5460287625).

Almost surely, 2^21113112121 is an apocalyptic number.

It is an amenable number.

21113112121 is a deficient number, since it is larger than the sum of its proper divisors (728038379).

21113112121 is an equidigital number, since it uses as much as digits as its factorization.

21113112121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 728038378.

The product of its digits is 24, while the sum is 16.

Adding to 21113112121 its reverse (12121131112), we get a palindrome (33234243233).

The spelling of 21113112121 in words is "twenty-one billion, one hundred thirteen million, one hundred twelve thousand, one hundred twenty-one".