840175 divided by 21 
Our goal is to divide 840175 by 21.

Step 1:
8 divided by 21 is 0 with a remainder of 8.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 8 and we're left with 8.
Include the next digit (4) from the dividend after 8, then repeat: 84 / 21

Let's proceed to step 2:
If we divide 84 by 21, we get 4 and a remainder of 0.
Write down 4 as next digit of the result. 
Result so far: 4.0
Deduct 84 from 84 and we're left with 0.
Bring next digit (0) of the dividend behind the 0 and repeat the process: 0 / 21

Moving on to step 3:
21 can be fit into 0 0 times, resulting in a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 40.0
Subtracting 0 from 0 leaves us 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.
Write down 0 as next digit of the result. 
Result so far: 400.0
If we take 0 away from 1, we end up with 1.
Grab the next digit (7) from the dividend, add it to 1, then carry on: 17 / 21

Going ahead to step 5:
The number 21 fits into 17 0 times, leaving a remainder of 17.
Record the quotient 0 as the next digit in the result. 
Result so far: 4000.0
The remainder is 17 after subtracting 0 from 17.
Bring next digit (5) of the dividend behind the 17 and repeat the process: 175 / 21

Step 6:
If we divide 175 by 21, we get 8 and a remainder of 7.
Record the quotient 8 as the next digit in the result. 
Result so far: 40008.0
Subtract 168 from 175 to get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Advancing to step 7:
If we divide 70 by 21, we get 3 and a remainder of 7.
Put 3 as the next digit of the answer. 
Result so far: 40008.3
If we subtract 63 from 70, we get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Step 8:
If we divide 70 by 21, we get 3 and a remainder of 7.
Put 3 as the next digit of the answer. 
Result so far: 40008.33
If we subtract 63 from 70, we get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

The final outcome is 40008.33, with a leftover of 0.007.