We're dividing 853431 by 21 
Let's see how many times 21 fits into 853431.

On to step 1:
If we divide 8 by 21, we get 0 and a remainder of 8.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 8 leaves us with 8.
Grab the next digit (5) from the dividend, add it to 8, then carry on: 85 / 21

Going ahead to step 2:
21 can be fit into 85 4 times, resulting in a remainder of 1.
The next digit of our result is 4. 
Result so far: 4.0
Deduct 84 from 85 and we're left with 1.
Take the next digit (3) from the dividend and append it to 1, then repeat: 13 / 21

Moving on to step 3:
The number 21 fits into 13 0 times, leaving a remainder of 13.
The number 0 becomes the next digit in our result. 
Result so far: 40.0
Deduct 0 from 13 and we're left with 13.
Bring next digit (4) of the dividend behind the 13 and repeat the process: 134 / 21

On to step 4:
134 divided by 21 is 6 with a remainder of 8.
Record the quotient 6 as the next digit in the result. 
Result so far: 406.0
Deduct 126 from 134 and we're left with 8.
Take the next digit (3) from the dividend and append it to 8, then repeat: 83 / 21

Moving on to step 5:
When dividing 83 by 21, we get 3 with a remainder of 20.
Record the quotient 3 as the next digit in the result. 
Result so far: 4063.0
If we take 63 away from 83, we end up with 20.
Bring next digit (1) of the dividend behind the 20 and repeat the process: 201 / 21

Going ahead to step 6:
21 can be fit into 201 9 times, resulting in a remainder of 12.
The number 9 becomes the next digit in our result. 
Result so far: 40639.0
If we take 189 away from 201, we end up with 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 7:
When dividing 120 by 21, we get 5 with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 40639.5
Subtracting 105 from 120 leaves us with 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 8:
21 goes into 150 7 times with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 40639.57
The remainder is 3 after subtracting 147 from 150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Moving on to step 9:
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: 40639.571
Subtracting 21 from 30 leaves us 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.

Advancing to step 10:
21 can be fit into 90 4 times, resulting in a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 40639.5714
If we take 84 away from 90, we end up with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Moving on to step 11:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 40639.57142
Subtracting 42 from 60 leaves us 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.

Step 12:
180 divided by 21 is 8 with a remainder of 12.
The next digit of our result is 8. 
Result so far: 40639.571428
The remainder is 12 after subtracting 168 from 180.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Advancing to step 13:
If we divide 120 by 21, we get 5 and a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 40639.5714285
If we subtract 105 from 120, we 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.

Let's proceed to step 14:
If we divide 150 by 21, we get 7 and a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 40639.57142857
Subtracting 147 from 150 leaves us with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Our division results in 40639.57142857 with a remaining 3e-09.