21145224 has 64 divisors (see below), whose sum is σ = 55319040. Its totient is φ = 6727680.

The previous prime is 21145213. The next prime is 21145249. The reversal of 21145224 is 42254112.

It is a self number, because there is not a number n which added to its sum of digits gives 21145224.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 72022 + ... + 72314.

It is an arithmetic number, because the mean of its divisors is an integer number (864360).

Almost surely, 2^21145224 is an apocalyptic number.

21145224 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21145224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27659520).

21145224 is an abundant number, since it is smaller than the sum of its proper divisors (34173816).

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

21145224 is a wasteful number, since it uses less digits than its factorization.

21145224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 430 (or 426 counting only the distinct ones).

The product of its digits is 640, while the sum is 21.

The square root of 21145224 is about 4598.3936325634. The cubic root of 21145224 is about 276.5269286754.

Adding to 21145224 its reverse (42254112), we get a palindrome (63399336).

The spelling of 21145224 in words is "twenty-one million, one hundred forty-five thousand, two hundred twenty-four".