21324221 has 2 divisors, whose sum is σ = 21324222. Its totient is φ = 21324220.

The previous prime is 21324203. The next prime is 21324227. The reversal of 21324221 is 12242312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13980121 + 7344100 = 3739^2 + 2710^2 .

It is a cyclic number.

It is not a de Polignac number, because 21324221 - 2¹⁸ = 21062077 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21324221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21324227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10662110 + 10662111.

It is an arithmetic number, because the mean of its divisors is an integer number (10662111).

Almost surely, 2^21324221 is an apocalyptic number.

It is an amenable number.

21324221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21324221 is an equidigital number, since it uses as much as digits as its factorization.

21324221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 192, while the sum is 17.

The square root of 21324221 is about 4617.8156091382. The cubic root of 21324221 is about 277.3050157475.

Adding to 21324221 its reverse (12242312), we get a palindrome (33566533).

The spelling of 21324221 in words is "twenty-one million, three hundred twenty-four thousand, two hundred twenty-one".