We're dividing 509571 by 21 
We're looking to find how many times 21 goes into 509571.

Going ahead to step 1:
21 can be fit into 5 0 times, resulting in a remainder of 5.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 5 and we're left with 5.
Append the next digit (0) from the dividend to 5 and continue with: 50 / 21

Let's proceed to step 2:
The number 21 fits into 50 2 times, leaving a remainder of 8.
The next digit of our result is 2. 
Result so far: 2.0
If we take 42 away from 50, we end up with 8.
Include the next digit (9) from the dividend after 8, then repeat: 89 / 21

Let's proceed to step 3:
When dividing 89 by 21, we get 4 with a remainder of 5.
Record the quotient 4 as the next digit in the result. 
Result so far: 24.0
The remainder is 5 after subtracting 84 from 89.
Include the next digit (5) from the dividend after 5, then repeat: 55 / 21

Going ahead to step 4:
21 can be fit into 55 2 times, resulting in a remainder of 13.
Record the quotient 2 as the next digit in the result. 
Result so far: 242.0
Subtract 42 from 55 to get 13.
Append the next digit (7) from the dividend to 13 and continue with: 137 / 21

Going ahead to step 5:
21 goes into 137 6 times with a remainder of 11.
Put 6 as the next digit of the answer. 
Result so far: 2426.0
Subtract 126 from 137 to get 11.
Fetch the next digit (1) from the dividend, attach it to 11 and continue: 111 / 21

Advancing to step 6:
111 divided by 21 is 5 with a remainder of 6.
Use 5 as the next digit of our solution. 
Result so far: 24265.0
If we take 105 away from 111, we end up with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 7:
If we divide 60 by 21, we get 2 and a remainder of 18.
The number 2 becomes the next digit in our result. 
Result so far: 24265.2
If we subtract 42 from 60, we get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

On to step 8:
If we divide 180 by 21, we get 8 and a remainder of 12.
The next digit of our result is 8. 
Result so far: 24265.28
Deduct 168 from 180 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Going ahead to step 9:
When dividing 120 by 21, we get 5 with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 24265.285
The remainder is 15 after subtracting 105 from 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Step 10:
150 divided by 21 is 7 with a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 24265.2857
Subtracting 147 from 150 leaves us with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Moving on to step 11:
21 goes into 30 1 times with a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 24265.28571
If we take 21 away from 30, we end up with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 12:
If we divide 90 by 21, we get 4 and a remainder of 6.
The next digit of our result is 4. 
Result so far: 24265.285714
If we take 84 away from 90, we end up with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Moving on to step 13:
21 goes into 60 2 times with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 24265.2857142
The remainder is 18 after subtracting 42 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

On to step 14:
When dividing 180 by 21, we get 8 with a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 24265.28571428
The remainder is 12 after subtracting 168 from 180.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

After the division, we end up with 24265.28571428 and a remainder of 1.2e-08.