21211221112121 has 4 divisors (see below), whose sum is σ = 21286705885044. Its totient is φ = 21135736339200.

The previous prime is 21211221112073. The next prime is 21211221112129. The reversal of 21211221112121 is 12121112211212.

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 7497678999721 + 13713542112400 = 2738189^2 + 3703180^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211221112121 - 2¹⁰ = 21211221111097 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21211221112093 and 21211221112102.

It is not an unprimeable number, because it can be changed into a prime (21211221112129) 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, 37742386040 + ... + 37742386601.

It is an arithmetic number, because the mean of its divisors is an integer number (5321676471261).

Almost surely, 2^{21211221112121} is an apocalyptic number.

It is an amenable number.

21211221112121 is a deficient number, since it is larger than the sum of its proper divisors (75484772923).

21211221112121 is an equidigital number, since it uses as much as digits as its factorization.

21211221112121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75484772922.

The product of its digits is 64, while the sum is 20.

Adding to 21211221112121 its reverse (12121112211212), we get a palindrome (33332333323333).

The spelling of 21211221112121 in words is "twenty-one trillion, two hundred eleven billion, two hundred twenty-one million, one hundred twelve thousand, one hundred twenty-one".