We're dividing 528759 by 21 
We want to figure out the number of times 528759 can be divided by 21.

Advancing to step 1:
5 divided by 21 is 0 with a remainder of 5.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 5 leaves us with 5.
Fetch the next digit (2) from the dividend, attach it to 5 and continue: 52 / 21

Going ahead to step 2:
52 divided by 21 is 2 with a remainder of 10.
The next digit of our result is 2. 
Result so far: 2.0
The remainder is 10 after subtracting 42 from 52.
Append the next digit (8) from the dividend to 10 and continue with: 108 / 21

On to step 3:
21 can be fit into 108 5 times, resulting in a remainder of 3.
Write down 5 as next digit of the result. 
Result so far: 25.0
If we take 105 away from 108, we end up with 3.
Fetch the next digit (7) from the dividend, attach it to 3 and continue: 37 / 21

Going ahead to step 4:
If we divide 37 by 21, we get 1 and a remainder of 16.
The next digit of our result is 1. 
Result so far: 251.0
Subtract 21 from 37 to get 16.
Append the next digit (5) from the dividend to 16 and continue with: 165 / 21

Step 5:
When dividing 165 by 21, we get 7 with a remainder of 18.
Put 7 as the next digit of the answer. 
Result so far: 2517.0
If we subtract 147 from 165, we get 18.
Include the next digit (9) from the dividend after 18, then repeat: 189 / 21

Going ahead to step 6:
The number 21 fits into 189 9 times, leaving a remainder of 0.
Write down 9 as next digit of the result. 
Result so far: 25179.0
Subtract 189 from 189 to get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

On to step 7:
The number 21 fits into 0 0 times, leaving a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 25179.0
If we subtract 0 from 0, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Advancing to step 8:
0 divided by 21 is 0 with a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 25179.0
If we subtract 0 from 0, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The final outcome is 25179.0, with a leftover of 0.0.