21210202121 has 4 divisors (see below), whose sum is σ = 21210747600. Its totient is φ = 21209656644.

The previous prime is 21210202063. The next prime is 21210202141. The reversal of 21210202121 is 12120201212.

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 21210202121 - 2¹⁰ = 21210201097 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21210202096 and 21210202105.

It is not an unprimeable number, because it can be changed into a prime (21210202141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 209531 + ... + 293808.

It is an arithmetic number, because the mean of its divisors is an integer number (5302686900).

Almost surely, 2^21210202121 is an apocalyptic number.

It is an amenable number.

21210202121 is a deficient number, since it is larger than the sum of its proper divisors (545479).

21210202121 is an equidigital number, since it uses as much as digits as its factorization.

21210202121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 545478.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21210202121 its reverse (12120201212), we get a palindrome (33330403333).

Subtracting from 21210202121 its reverse (12120201212), we obtain a palindrome (9090000909).

The spelling of 21210202121 in words is "twenty-one billion, two hundred ten million, two hundred two thousand, one hundred twenty-one".