We look at the division of 421864 by 21 
We want to divide 421864 by 21.

Moving on to step 1:
If we divide 4 by 21, we get 0 and a remainder of 4.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 4, we end up with 4.
Take the next digit (2) from the dividend and append it to 4, then repeat: 42 / 21

On to step 2:
The number 21 fits into 42 2 times, leaving a remainder of 0.
Put 2 as the next digit of the answer. 
Result so far: 2.0
If we subtract 42 from 42, we get 0.
Bring next digit (1) of the dividend behind the 0 and repeat the process: 1 / 21

Going ahead to step 3:
1 divided by 21 is 0 with a remainder of 1.
The next digit of our result is 0. 
Result so far: 20.0
The remainder is 1 after subtracting 0 from 1.
Bring next digit (8) of the dividend behind the 1 and repeat the process: 18 / 21

Advancing to step 4:
18 divided by 21 is 0 with a remainder of 18.
The next digit of our result is 0. 
Result so far: 200.0
If we take 0 away from 18, we end up with 18.
Fetch the next digit (6) from the dividend, attach it to 18 and continue: 186 / 21

Going ahead to step 5:
If we divide 186 by 21, we get 8 and a remainder of 18.
The number 8 becomes the next digit in our result. 
Result so far: 2008.0
If we take 168 away from 186, we end up with 18.
Include the next digit (4) from the dividend after 18, then repeat: 184 / 21

On to step 6:
184 divided by 21 is 8 with a remainder of 16.
Write down 8 as next digit of the result. 
Result so far: 20088.0
Subtract 168 from 184 to get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Step 7:
21 goes into 160 7 times with a remainder of 13.
Write down 7 as next digit of the result. 
Result so far: 20088.7
Subtract 147 from 160 to get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Going ahead to step 8:
The number 21 fits into 130 6 times, leaving a remainder of 4.
The number 6 becomes the next digit in our result. 
Result so far: 20088.76
Subtract 126 from 130 to get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 9:
If we divide 40 by 21, we get 1 and a remainder of 19.
Record the quotient 1 as the next digit in the result. 
Result so far: 20088.761
The remainder is 19 after subtracting 21 from 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 10:
If we divide 190 by 21, we get 9 and a remainder of 1.
Record the quotient 9 as the next digit in the result. 
Result so far: 20088.7619
If we subtract 189 from 190, we get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Moving on to step 11:
If we divide 10 by 21, we get 0 and a remainder of 10.
Record the quotient 0 as the next digit in the result. 
Result so far: 20088.7619
If we subtract 0 from 10, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Moving on to step 12:
100 divided by 21 is 4 with a remainder of 16.
Use 4 as the next digit of our solution. 
Result so far: 20088.761904
Subtracting 84 from 100 leaves us with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Going ahead to step 13:
When dividing 160 by 21, we get 7 with a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 20088.7619047
If we subtract 147 from 160, we get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Going ahead to step 14:
21 can be fit into 130 6 times, resulting in a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 20088.76190476
The remainder is 4 after subtracting 126 from 130.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Our division results in 20088.76190476 with a remaining 4e-09.