We divide 339663 by 21
Our goal is to divide 339663 by 21.

Let's proceed to step 1:
The number 21 fits into 3 0 times, leaving a remainder of 3.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 3 after subtracting 0 from 3.
Take the next digit (3) from the dividend and append it to 3, then repeat: 33 / 21

On to step 2:
21 goes into 33 1 times with a remainder of 12.
Write down 1 as next digit of the result. 
Result so far: 1.0
If we subtract 21 from 33, we get 12.
Fetch the next digit (9) from the dividend, attach it to 12 and continue: 129 / 21

Advancing to step 3:
21 can be fit into 129 6 times, resulting in a remainder of 3.
The number 6 becomes the next digit in our result. 
Result so far: 16.0
Deduct 126 from 129 and we're left with 3.
Fetch the next digit (6) from the dividend, attach it to 3 and continue: 36 / 21

Let's proceed to step 4:
21 can be fit into 36 1 times, resulting in a remainder of 15.
The number 1 becomes the next digit in our result. 
Result so far: 161.0
Subtracting 21 from 36 leaves us with 15.
Grab the next digit (6) from the dividend, add it to 15, then carry on: 156 / 21

Step 5:
If we divide 156 by 21, we get 7 and a remainder of 9.
Record the quotient 7 as the next digit in the result. 
Result so far: 1617.0
Deduct 147 from 156 and we're left with 9.
Include the next digit (3) from the dividend after 9, then repeat: 93 / 21

Advancing to step 6:
The number 21 fits into 93 4 times, leaving a remainder of 9.
The number 4 becomes the next digit in our result. 
Result so far: 16174.0
If we take 84 away from 93, we end up 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.

On to step 7:
21 goes into 90 4 times with a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 16174.4
If we subtract 84 from 90, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 8:
60 divided by 21 is 2 with a remainder of 18.
The number 2 becomes the next digit in our result. 
Result so far: 16174.42
The remainder is 18 after subtracting 42 from 60.
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 9:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 16174.428
Subtract 168 from 180 to 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.

Let's proceed to step 10:
If we divide 120 by 21, we get 5 and a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 16174.4285
Deduct 105 from 120 and we're left 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.

Going ahead to step 11:
21 can be fit into 150 7 times, resulting in a remainder of 3.
The next digit of our result is 7. 
Result so far: 16174.42857
Subtract 147 from 150 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Let's proceed to step 12:
21 goes into 30 1 times with a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 16174.428571
If we take 21 away from 30, we end up 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 13:
When dividing 90 by 21, we get 4 with a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 16174.4285714
The remainder is 6 after subtracting 84 from 90.
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 14:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 16174.42857142
The remainder is 18 after subtracting 42 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

The final result is 16174.42857142 with a remainder of 1.8e-08.