21210323221 has 4 divisors (see below), whose sum is σ = 21233155500. Its totient is φ = 21187490944.

The previous prime is 21210323209. The next prime is 21210323269. The reversal of 21210323221 is 12232301212.

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 957902500 + 20252420721 = 30950^2 + 142311^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210323221 - 2¹¹ = 21210321173 is a prime.

It is a super-2 number, since 2×21210323221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210323291) 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, 11414746 + ... + 11416603.

It is an arithmetic number, because the mean of its divisors is an integer number (5308288875).

Almost surely, 2^21210323221 is an apocalyptic number.

It is an amenable number.

21210323221 is a deficient number, since it is larger than the sum of its proper divisors (22832279).

21210323221 is an equidigital number, since it uses as much as digits as its factorization.

21210323221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22832278.

The product of its (nonzero) digits is 288, while the sum is 19.

Adding to 21210323221 its reverse (12232301212), we get a palindrome (33442624433).

The spelling of 21210323221 in words is "twenty-one billion, two hundred ten million, three hundred twenty-three thousand, two hundred twenty-one".