21220331221 has 4 divisors (see below), whose sum is σ = 21247926700. Its totient is φ = 21192735744.

The previous prime is 21220331179. The next prime is 21220331227. The reversal of 21220331221 is 12213302212.

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 10572980625 + 10647350596 = 102825^2 + 103186^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220331221 - 2¹¹ = 21220329173 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21220331227) 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, 13796586 + ... + 13798123.

It is an arithmetic number, because the mean of its divisors is an integer number (5311981675).

Almost surely, 2^21220331221 is an apocalyptic number.

It is an amenable number.

21220331221 is a deficient number, since it is larger than the sum of its proper divisors (27595479).

21220331221 is an equidigital number, since it uses as much as digits as its factorization.

21220331221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27595478.

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

Adding to 21220331221 its reverse (12213302212), we get a palindrome (33433633433).

The spelling of 21220331221 in words is "twenty-one billion, two hundred twenty million, three hundred thirty-one thousand, two hundred twenty-one".