21228289 has 2 divisors, whose sum is σ = 21228290. Its totient is φ = 21228288.

The previous prime is 21228247. The next prime is 21228307. The reversal of 21228289 is 98282212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14938225 + 6290064 = 3865^2 + 2508^2 .

It is a cyclic number.

It is not a de Polignac number, because 21228289 - 2¹¹ = 21226241 is a prime.

It is not a weakly prime, because it can be changed into another prime (21228209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10614144 + 10614145.

It is an arithmetic number, because the mean of its divisors is an integer number (10614145).

Almost surely, 2^21228289 is an apocalyptic number.

It is an amenable number.

21228289 is a deficient number, since it is larger than the sum of its proper divisors (1).

21228289 is an equidigital number, since it uses as much as digits as its factorization.

21228289 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9216, while the sum is 34.

The square root of 21228289 is about 4607.4167382602. The cubic root of 21228289 is about 276.8885500896. Note that the first 3 decimals are identical.

The spelling of 21228289 in words is "twenty-one million, two hundred twenty-eight thousand, two hundred eighty-nine".