We divide 519785 by 21
The aim is to understand the frequency of 21 in 519785.

Let's proceed to step 1:
The number 21 fits into 5 0 times, leaving a remainder of 5.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 5 to get 5.
Fetch the next digit (1) from the dividend, attach it to 5 and continue: 51 / 21

Moving on to step 2:
21 goes into 51 2 times with a remainder of 9.
The number 2 becomes the next digit in our result. 
Result so far: 2.0
If we subtract 42 from 51, we get 9.
Include the next digit (9) from the dividend after 9, then repeat: 99 / 21

Moving on to step 3:
The number 21 fits into 99 4 times, leaving a remainder of 15.
The number 4 becomes the next digit in our result. 
Result so far: 24.0
Deduct 84 from 99 and we're left with 15.
Take the next digit (7) from the dividend and append it to 15, then repeat: 157 / 21

Let's proceed to step 4:
21 can be fit into 157 7 times, resulting in a remainder of 10.
Write down 7 as next digit of the result. 
Result so far: 247.0
If we subtract 147 from 157, we get 10.
Bring next digit (8) of the dividend behind the 10 and repeat the process: 108 / 21

Step 5:
21 goes into 108 5 times with a remainder of 3.
Put 5 as the next digit of the answer. 
Result so far: 2475.0
If we take 105 away from 108, we end up with 3.
Append the next digit (5) from the dividend to 3 and continue with: 35 / 21

On to step 6:
21 can be fit into 35 1 times, resulting in a remainder of 14.
The next digit of our result is 1. 
Result so far: 24751.0
Subtract 21 from 35 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.

Moving on to step 7:
If we divide 140 by 21, we get 6 and a remainder of 14.
Put 6 as the next digit of the answer. 
Result so far: 24751.6
If we take 126 away from 140, we end up 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.

Advancing to step 8:
When dividing 140 by 21, we get 6 with a remainder of 14.
The number 6 becomes the next digit in our result. 
Result so far: 24751.66
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.

The final outcome is 24751.66, with a leftover of 0.014.