Let's divide 87137402 by 21
We want to divide 87137402 by 21.

Step 1:
21 can be fit into 8 0 times, resulting in a remainder of 8.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 8 to get 8.
Fetch the next digit (7) from the dividend, attach it to 8 and continue: 87 / 21

Advancing to step 2:
21 goes into 87 4 times with a remainder of 3.
Record the quotient 4 as the next digit in the result. 
Result so far: 4.0
The remainder is 3 after subtracting 84 from 87.
Bring next digit (1) of the dividend behind the 3 and repeat the process: 31 / 21

Moving on to step 3:
31 divided by 21 is 1 with a remainder of 10.
The next digit of our result is 1. 
Result so far: 41.0
Deduct 21 from 31 and we're left with 10.
Take the next digit (3) from the dividend and append it to 10, then repeat: 103 / 21

On to step 4:
21 goes into 103 4 times with a remainder of 19.
The number 4 becomes the next digit in our result. 
Result so far: 414.0
Subtract 84 from 103 to get 19.
Take the next digit (7) from the dividend and append it to 19, then repeat: 197 / 21

Step 5:
The number 21 fits into 197 9 times, leaving a remainder of 8.
Write down 9 as next digit of the result. 
Result so far: 4149.0
If we take 189 away from 197, we end up with 8.
Bring next digit (4) of the dividend behind the 8 and repeat the process: 84 / 21

Going ahead to step 6:
21 goes into 84 4 times with a remainder of 0.
Use 4 as the next digit of our solution. 
Result so far: 41494.0
Deduct 84 from 84 and we're left with 0.
Include the next digit (0) from the dividend after 0, then repeat: 0 / 21

Going ahead to step 7:
0 divided by 21 is 0 with a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 414940.0
If we subtract 0 from 0, we get 0.
Grab the next digit (2) from the dividend, add it to 0, then carry on: 2 / 21

Going ahead to step 8:
When dividing 2 by 21, we get 0 with a remainder of 2.
Use 0 as the next digit of our solution. 
Result so far: 4149400.0
If we subtract 0 from 2, we get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 9:
If we divide 20 by 21, we get 0 and a remainder of 20.
Write down 0 as next digit of the result. 
Result so far: 4149400.0
Subtracting 0 from 20 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 10:
200 divided by 21 is 9 with a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 4149400.09
The remainder is 11 after subtracting 189 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Going ahead to step 11:
21 can be fit into 110 5 times, resulting in a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 4149400.095
Deduct 105 from 110 and we're left with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Moving on to step 12:
50 divided by 21 is 2 with a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 4149400.0952
Subtract 42 from 50 to get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Step 13:
21 goes into 80 3 times with a remainder of 17.
Record the quotient 3 as the next digit in the result. 
Result so far: 4149400.09523
Subtracting 63 from 80 leaves us with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Moving on to step 14:
21 can be fit into 170 8 times, resulting in a remainder of 2.
The number 8 becomes the next digit in our result. 
Result so far: 4149400.095238
Subtract 168 from 170 to get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Step 15:
If we divide 20 by 21, we get 0 and a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 4149400.095238
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Let's proceed to step 16:
If we divide 200 by 21, we get 9 and a remainder of 11.
Use 9 as the next digit of our solution. 
Result so far: 4149400.09523809
Subtracting 189 from 200 leaves us with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

The final outcome is 4149400.09523809, with a leftover of 1.1e-08.