Let's divide 478520 by 21
The aim is to understand the frequency of 21 in 478520.

On to step 1:
21 can be fit into 4 0 times, resulting in a remainder of 4.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we subtract 0 from 4, we get 4.
Append the next digit (7) from the dividend to 4 and continue with: 47 / 21

Going ahead to step 2:
When dividing 47 by 21, we get 2 with a remainder of 5.
Record the quotient 2 as the next digit in the result. 
Result so far: 2.0
If we subtract 42 from 47, we get 5.
Bring next digit (8) of the dividend behind the 5 and repeat the process: 58 / 21

Let's proceed to step 3:
21 goes into 58 2 times with a remainder of 16.
Record the quotient 2 as the next digit in the result. 
Result so far: 22.0
The remainder is 16 after subtracting 42 from 58.
Include the next digit (5) from the dividend after 16, then repeat: 165 / 21

Advancing to step 4:
21 can be fit into 165 7 times, resulting in a remainder of 18.
Write down 7 as next digit of the result. 
Result so far: 227.0
The remainder is 18 after subtracting 147 from 165.
Fetch the next digit (2) from the dividend, attach it to 18 and continue: 182 / 21

Advancing to step 5:
The number 21 fits into 182 8 times, leaving a remainder of 14.
Put 8 as the next digit of the answer. 
Result so far: 2278.0
Deduct 168 from 182 and we're left with 14.
Bring next digit (0) of the dividend behind the 14 and repeat the process: 140 / 21

Going ahead to step 6:
The number 21 fits into 140 6 times, leaving a remainder of 14.
Put 6 as the next digit of the answer. 
Result so far: 22786.0
Subtract 126 from 140 to get 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Let's proceed to step 7:
140 divided by 21 is 6 with a remainder of 14.
Use 6 as the next digit of our solution. 
Result so far: 22786.6
Subtracting 126 from 140 leaves us with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

On to step 8:
21 goes into 140 6 times with a remainder of 14.
The next digit of our result is 6. 
Result so far: 22786.66
The remainder is 14 after subtracting 126 from 140.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

In conclusion, the division gives 22786.66 with a balance of 0.014.