21324509 has 2 divisors, whose sum is σ = 21324510. Its totient is φ = 21324508.

The previous prime is 21324503. The next prime is 21324529. The reversal of 21324509 is 90542312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21187609 + 136900 = 4603^2 + 370^2 .

It is a cyclic number.

It is not a de Polignac number, because 21324509 - 2⁸ = 21324253 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21324503) 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, 10662254 + 10662255.

It is an arithmetic number, because the mean of its divisors is an integer number (10662255).

Almost surely, 2^21324509 is an apocalyptic number.

It is an amenable number.

21324509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21324509 is an equidigital number, since it uses as much as digits as its factorization.

21324509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 21324509 is about 4617.8467926080. The cubic root of 21324509 is about 277.3062641477.

The spelling of 21324509 in words is "twenty-one million, three hundred twenty-four thousand, five hundred nine".