21202121220121 has 4 divisors (see below), whose sum is σ = 21222527497600. Its totient is φ = 21181714942644.

The previous prime is 21202121220103. The next prime is 21202121220143. The reversal of 21202121220121 is 12102212120212.

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 a cyclic number.

It is not a de Polignac number, because 21202121220121 - 2¹⁵ = 21202121187353 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21202121220101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10203137181 + ... + 10203139258.

It is an arithmetic number, because the mean of its divisors is an integer number (5305631874400).

Almost surely, 2^{21202121220121} is an apocalyptic number.

It is an amenable number.

21202121220121 is a deficient number, since it is larger than the sum of its proper divisors (20406277479).

21202121220121 is a wasteful number, since it uses less digits than its factorization.

21202121220121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20406277478.

The product of its (nonzero) digits is 128, while the sum is 19.

Adding to 21202121220121 its reverse (12102212120212), we get a palindrome (33304333340333).

Subtracting from 21202121220121 its reverse (12102212120212), we obtain a palindrome (9099909099909).

The spelling of 21202121220121 in words is "twenty-one trillion, two hundred two billion, one hundred twenty-one million, two hundred twenty thousand, one hundred twenty-one".