21320444221 has 2 divisors, whose sum is σ = 21320444222. Its totient is φ = 21320444220.

The previous prime is 21320444203. The next prime is 21320444267. The reversal of 21320444221 is 12244402312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21319212121 + 1232100 = 146011^2 + 1110^2 .

It is a cyclic number.

It is not a de Polignac number, because 21320444221 - 2¹⁷ = 21320313149 is a prime.

It is a super-2 number, since 2×21320444221² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21320444291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660222110 + 10660222111.

It is an arithmetic number, because the mean of its divisors is an integer number (10660222111).

Almost surely, 2^21320444221 is an apocalyptic number.

It is an amenable number.

21320444221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320444221 is an equidigital number, since it uses as much as digits as its factorization.

21320444221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3072, while the sum is 25.

Adding to 21320444221 its reverse (12244402312), we get a palindrome (33564846533).

The spelling of 21320444221 in words is "twenty-one billion, three hundred twenty million, four hundred forty-four thousand, two hundred twenty-one".