We look at the division of 793863 by 21 
Let's see how many times 21 fits into 793863.

On to step 1:
The number 21 fits into 7 0 times, leaving a remainder of 7.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 7 leaves us with 7.
Take the next digit (9) from the dividend and append it to 7, then repeat: 79 / 21

Moving on to step 2:
21 can be fit into 79 3 times, resulting in a remainder of 16.
Write down 3 as next digit of the result. 
Result so far: 3.0
The remainder is 16 after subtracting 63 from 79.
Bring next digit (3) of the dividend behind the 16 and repeat the process: 163 / 21

Step 3:
21 goes into 163 7 times with a remainder of 16.
The number 7 becomes the next digit in our result. 
Result so far: 37.0
If we take 147 away from 163, we end up with 16.
Append the next digit (8) from the dividend to 16 and continue with: 168 / 21

On to step 4:
The number 21 fits into 168 8 times, leaving a remainder of 0.
The next digit of our result is 8. 
Result so far: 378.0
If we subtract 168 from 168, we get 0.
Take the next digit (6) from the dividend and append it to 0, then repeat: 6 / 21

Step 5:
The number 21 fits into 6 0 times, leaving a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 3780.0
Deduct 0 from 6 and we're left with 6.
Bring next digit (3) of the dividend behind the 6 and repeat the process: 63 / 21

On to step 6:
If we divide 63 by 21, we get 3 and a remainder of 0.
Record the quotient 3 as the next digit in the result. 
Result so far: 37803.0
Subtracting 63 from 63 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Going ahead to step 7:
When dividing 0 by 21, we get 0 with a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 37803.0
If we take 0 away from 0, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Going ahead to step 8:
0 divided by 21 is 0 with a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 37803.0
If we take 0 away from 0, we end up with 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 result is 37803.0 with a remainder of 0.0.