21189221 has 2 divisors, whose sum is σ = 21189222. Its totient is φ = 21189220.

The previous prime is 21189173. The next prime is 21189229. The reversal of 21189221 is 12298112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16924996 + 4264225 = 4114^2 + 2065^2 .

It is a cyclic number.

It is not a de Polignac number, because 21189221 - 2¹⁰ = 21188197 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21189229) 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, 10594610 + 10594611.

It is an arithmetic number, because the mean of its divisors is an integer number (10594611).

Almost surely, 2^21189221 is an apocalyptic number.

It is an amenable number.

21189221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21189221 is an equidigital number, since it uses as much as digits as its factorization.

21189221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 576, while the sum is 26.

The square root of 21189221 is about 4603.1750998631. The cubic root of 21189221 is about 276.7185862465.

The spelling of 21189221 in words is "twenty-one million, one hundred eighty-nine thousand, two hundred twenty-one".