21304355221 has 4 divisors (see below), whose sum is σ = 21492889452. Its totient is φ = 21115820992.

The previous prime is 21304355213. The next prime is 21304355279. The reversal of 21304355221 is 12255340312.

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 7723948996 + 13580406225 = 87886^2 + 116535^2 .

It is a cyclic number.

It is not a de Polignac number, because 21304355221 - 2³ = 21304355213 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 21304355221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21304352221) 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, 94266946 + ... + 94267171.

It is an arithmetic number, because the mean of its divisors is an integer number (5373222363).

Almost surely, 2^21304355221 is an apocalyptic number.

It is an amenable number.

21304355221 is a deficient number, since it is larger than the sum of its proper divisors (188534231).

21304355221 is a wasteful number, since it uses less digits than its factorization.

21304355221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188534230.

The product of its (nonzero) digits is 7200, while the sum is 28.

Adding to 21304355221 its reverse (12255340312), we get a palindrome (33559695533).

The spelling of 21304355221 in words is "twenty-one billion, three hundred four million, three hundred fifty-five thousand, two hundred twenty-one".