We look at the division of 525156 by 21 
We're looking to find how many times 21 goes into 525156.

Advancing to step 1:
If we divide 5 by 21, we get 0 and 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.
Include the next digit (2) from the dividend after 5, then repeat: 52 / 21

Going ahead to step 2:
If we divide 52 by 21, we get 2 and a remainder of 10.
Write down 2 as next digit of the result. 
Result so far: 2.0
Subtract 42 from 52 to get 10.
Append the next digit (5) from the dividend to 10 and continue with: 105 / 21

Step 3:
21 can be fit into 105 5 times, resulting in a remainder of 0.
Put 5 as the next digit of the answer. 
Result so far: 25.0
Deduct 105 from 105 and we're left with 0.
Fetch the next digit (1) from the dividend, attach it to 0 and continue: 1 / 21

Moving on to step 4:
21 can be fit into 1 0 times, resulting in a remainder of 1.
The next digit of our result is 0. 
Result so far: 250.0
Deduct 0 from 1 and we're left with 1.
Grab the next digit (5) from the dividend, add it to 1, then carry on: 15 / 21

Moving on to step 5:
The number 21 fits into 15 0 times, leaving a remainder of 15.
Write down 0 as next digit of the result. 
Result so far: 2500.0
If we subtract 0 from 15, we get 15.
Fetch the next digit (6) from the dividend, attach it to 15 and continue: 156 / 21

Moving on to step 6:
156 divided by 21 is 7 with a remainder of 9.
Put 7 as the next digit of the answer. 
Result so far: 25007.0
If we subtract 147 from 156, we get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Moving on to step 7:
When dividing 90 by 21, we get 4 with a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 25007.4
The remainder is 6 after subtracting 84 from 90.
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 8:
When dividing 60 by 21, we get 2 with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 25007.42
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.

Let's proceed to step 9:
21 goes into 180 8 times with a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 25007.428
Subtract 168 from 180 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Let's proceed to step 10:
When dividing 120 by 21, we get 5 with a remainder of 15.
The next digit of our result is 5. 
Result so far: 25007.4285
Subtract 105 from 120 to get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Step 11:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 25007.42857
If we subtract 147 from 150, we get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Advancing to step 12:
If we divide 30 by 21, we get 1 and a remainder of 9.
The number 1 becomes the next digit in our result. 
Result so far: 25007.428571
Deduct 21 from 30 and we're left 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.

Going ahead to step 13:
90 divided by 21 is 4 with a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 25007.4285714
If we subtract 84 from 90, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Let's proceed to step 14:
60 divided by 21 is 2 with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 25007.42857142
Deduct 42 from 60 and we're left with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

After the division, we end up with 25007.42857142 and a remainder of 1.8e-08.