21824213 has 4 divisors (see below), whose sum is σ = 21833580. Its totient is φ = 21814848.

The previous prime is 21824203. The next prime is 21824221. The reversal of 21824213 is 31242812.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 18164644 + 3659569 = 4262^2 + 1913^2 .

It is a cyclic number.

It is not a de Polignac number, because 21824213 - 2⁴ = 21824197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21824203) 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 in 3 ways as a sum of consecutive naturals, for example, 1853 + ... + 6861.

It is an arithmetic number, because the mean of its divisors is an integer number (5458395).

Almost surely, 2^21824213 is an apocalyptic number.

It is an amenable number.

21824213 is a deficient number, since it is larger than the sum of its proper divisors (9367).

21824213 is an equidigital number, since it uses as much as digits as its factorization.

21824213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9366.

The product of its digits is 768, while the sum is 23.

The square root of 21824213 is about 4671.6392198028. The cubic root of 21824213 is about 279.4556302596.

The spelling of 21824213 in words is "twenty-one million, eight hundred twenty-four thousand, two hundred thirteen".