We look at the division of 343608 by 21 
We want to divide 343608 by 21.

Going ahead to step 1:
When dividing 3 by 21, we get 0 with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Fetch the next digit (4) from the dividend, attach it to 3 and continue: 34 / 21

Step 2:
21 can be fit into 34 1 times, resulting in a remainder of 13.
The next digit of our result is 1. 
Result so far: 1.0
Subtract 21 from 34 to get 13.
Bring next digit (3) of the dividend behind the 13 and repeat the process: 133 / 21

On to step 3:
The number 21 fits into 133 6 times, leaving a remainder of 7.
The number 6 becomes the next digit in our result. 
Result so far: 16.0
If we subtract 126 from 133, we get 7.
Fetch the next digit (6) from the dividend, attach it to 7 and continue: 76 / 21

On to step 4:
If we divide 76 by 21, we get 3 and a remainder of 13.
Write down 3 as next digit of the result. 
Result so far: 163.0
If we subtract 63 from 76, we get 13.
Append the next digit (0) from the dividend to 13 and continue with: 130 / 21

Advancing to step 5:
The number 21 fits into 130 6 times, leaving a remainder of 4.
The next digit of our result is 6. 
Result so far: 1636.0
Deduct 126 from 130 and we're left with 4.
Fetch the next digit (8) from the dividend, attach it to 4 and continue: 48 / 21

Let's proceed to step 6:
21 goes into 48 2 times with a remainder of 6.
Use 2 as the next digit of our solution. 
Result so far: 16362.0
The remainder is 6 after subtracting 42 from 48.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

On to step 7:
If we divide 60 by 21, we get 2 and a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 16362.2
If we take 42 away from 60, we end up 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.

On to step 8:
21 goes into 180 8 times with a remainder of 12.
The next digit of our result is 8. 
Result so far: 16362.28
If we take 168 away from 180, 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.

Step 9:
120 divided by 21 is 5 with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 16362.285
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.

Moving on to step 10:
21 goes into 150 7 times with a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 16362.2857
Deduct 147 from 150 and we're left 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.

Advancing to step 11:
If we divide 30 by 21, we get 1 and a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 16362.28571
If we subtract 21 from 30, we get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 12:
21 can be fit into 90 4 times, resulting in a remainder of 6.
The next digit of our result is 4. 
Result so far: 16362.285714
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 13:
21 can be fit into 60 2 times, resulting in a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 16362.2857142
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.

On to step 14:
180 divided by 21 is 8 with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 16362.28571428
If we subtract 168 from 180, we get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

The final result is 16362.28571428 with a remainder of 1.2e-08.