21020224 has 28 divisors (see below), whose sum is σ = 42505884. Its totient is φ = 10310144.

The previous prime is 21020161. The next prime is 21020227. The reversal of 21020224 is 42202012.

It can be written as a sum of positive squares in 2 ways, for example, as 11778624 + 9241600 = 3432^2 + 3040^2 .

It is not an unprimeable number, because it can be changed into a prime (21020227) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 294 + ... + 6490.

Almost surely, 2^21020224 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21020224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21252942).

21020224 is an abundant number, since it is smaller than the sum of its proper divisors (21485660).

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

21020224 is an equidigital number, since it uses as much as digits as its factorization.

21020224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6262 (or 6252 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 13.

The square root of 21020224 is about 4584.7817832477. The cubic root of 21020224 is about 275.9809550676.

Adding to 21020224 its reverse (42202012), we get a palindrome (63222236).

The spelling of 21020224 in words is "twenty-one million, twenty thousand, two hundred twenty-four".