21304109 has 2 divisors, whose sum is σ = 21304110. Its totient is φ = 21304108.

The previous prime is 21304097. The next prime is 21304117. The reversal of 21304109 is 90140312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20448484 + 855625 = 4522^2 + 925^2 .

It is a cyclic number.

It is not a de Polignac number, because 21304109 - 2⁴ = 21304093 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21304139) 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, 10652054 + 10652055.

It is an arithmetic number, because the mean of its divisors is an integer number (10652055).

Almost surely, 2^21304109 is an apocalyptic number.

It is an amenable number.

21304109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21304109 is an equidigital number, since it uses as much as digits as its factorization.

21304109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 21304109 is about 4615.6374424341. The cubic root of 21304109 is about 277.2178079855.

The spelling of 21304109 in words is "twenty-one million, three hundred four thousand, one hundred nine".