21130311221 has 4 divisors (see below), whose sum is σ = 21134534700. Its totient is φ = 21126087744.

The previous prime is 21130311113. The next prime is 21130311227. The reversal of 21130311221 is 12211303112.

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 15707608900 + 5422702321 = 125330^2 + 73639^2 .

It is a cyclic number.

It is not a de Polignac number, because 21130311221 - 2¹⁸ = 21130049077 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21130311221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21130311227) 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, 2104226 + ... + 2114243.

It is an arithmetic number, because the mean of its divisors is an integer number (5283633675).

Almost surely, 2^21130311221 is an apocalyptic number.

It is an amenable number.

21130311221 is a deficient number, since it is larger than the sum of its proper divisors (4223479).

21130311221 is an equidigital number, since it uses as much as digits as its factorization.

21130311221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4223478.

The product of its (nonzero) digits is 72, while the sum is 17.

Adding to 21130311221 its reverse (12211303112), we get a palindrome (33341614333).

The spelling of 21130311221 in words is "twenty-one billion, one hundred thirty million, three hundred eleven thousand, two hundred twenty-one".