21344209 has 2 divisors, whose sum is σ = 21344210. Its totient is φ = 21344208.

The previous prime is 21344173. The next prime is 21344237. The reversal of 21344209 is 90244312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19580625 + 1763584 = 4425^2 + 1328^2 .

It is a cyclic number.

It is not a de Polignac number, because 21344209 - 2⁹ = 21343697 is a prime.

It is equal to p_1350358 and since 21344209 and 1350358 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21344249) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10672104 + 10672105.

It is an arithmetic number, because the mean of its divisors is an integer number (10672105).

Almost surely, 2^21344209 is an apocalyptic number.

It is an amenable number.

21344209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21344209 is an equidigital number, since it uses as much as digits as its factorization.

21344209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 21344209 is about 4619.9793289581. The cubic root of 21344209 is about 277.3916315218.

The spelling of 21344209 in words is "twenty-one million, three hundred forty-four thousand, two hundred nine".