21504224 has 24 divisors (see below), whose sum is σ = 48385008. Its totient is φ = 9216000.

The previous prime is 21504199. The next prime is 21504227. The reversal of 21504224 is 42240512.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21504196 and 21504205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21504227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 47777 + ... + 48224.

It is an arithmetic number, because the mean of its divisors is an integer number (2016042).

Almost surely, 2^21504224 is an apocalyptic number.

It is an amenable number.

21504224 is an abundant number, since it is smaller than the sum of its proper divisors (26880784).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21504224 is an equidigital number, since it uses as much as digits as its factorization.

21504224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96018 (or 96010 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 21504224 is about 4637.2647110123. The cubic root of 21504224 is about 278.0830971505.

Adding to 21504224 its reverse (42240512), we get a palindrome (63744736).

The spelling of 21504224 in words is "twenty-one million, five hundred four thousand, two hundred twenty-four".