21824009 has 2 divisors, whose sum is σ = 21824010. Its totient is φ = 21824008.

The previous prime is 21823981. The next prime is 21824021. The reversal of 21824009 is 90042812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17935225 + 3888784 = 4235^2 + 1972^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21824009 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a plaindrome in base 11.

It is not a weakly prime, because it can be changed into another prime (21824069) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10912004 + 10912005.

It is an arithmetic number, because the mean of its divisors is an integer number (10912005).

Almost surely, 2^21824009 is an apocalyptic number.

It is an amenable number.

21824009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21824009 is an equidigital number, since it uses as much as digits as its factorization.

21824009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 21824009 is about 4671.6173858740. The cubic root of 21824009 is about 279.4547595275.

The spelling of 21824009 in words is "twenty-one million, eight hundred twenty-four thousand, nine".