21820224 has 28 divisors (see below), whose sum is σ = 57733184. Its totient is φ = 7273344.

The previous prime is 21820213. The next prime is 21820243. The reversal of 21820224 is 42202812.

It is a happy number.

It is a super-2 number, since 2×21820224² = 952244350820352, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21820224.

It is a congruent number.

It is an unprimeable number.

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, 56632 + ... + 57015.

Almost surely, 2^21820224 is an apocalyptic number.

21820224 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21820224 is an abundant number, since it is smaller than the sum of its proper divisors (35912960).

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

21820224 is a wasteful number, since it uses less digits than its factorization.

21820224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 113662 (or 113652 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 21.

The square root of 21820224 is about 4671.2122623576. The cubic root of 21820224 is about 279.4386030486.

The spelling of 21820224 in words is "twenty-one million, eight hundred twenty thousand, two hundred twenty-four".