We look at the division of 139657 by 21 
Let's see how many times 21 fits into 139657.

Advancing to step 1:
1 divided by 21 is 0 with a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Grab the next digit (3) from the dividend, add it to 1, then carry on: 13 / 21

On to step 2:
If we divide 13 by 21, we get 0 and a remainder of 13.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 13 after subtracting 0 from 13.
Fetch the next digit (9) from the dividend, attach it to 13 and continue: 139 / 21

Let's proceed to step 3:
139 divided by 21 is 6 with a remainder of 13.
The number 6 becomes the next digit in our result. 
Result so far: 6.0
Subtracting 126 from 139 leaves us with 13.
Take the next digit (6) from the dividend and append it to 13, then repeat: 136 / 21

On to step 4:
136 divided by 21 is 6 with a remainder of 10.
Write down 6 as next digit of the result. 
Result so far: 66.0
The remainder is 10 after subtracting 126 from 136.
Include the next digit (5) from the dividend after 10, then repeat: 105 / 21

Moving on to step 5:
If we divide 105 by 21, we get 5 and a remainder of 0.
The next digit of our result is 5. 
Result so far: 665.0
Subtracting 105 from 105 leaves us with 0.
Take the next digit (7) from the dividend and append it to 0, then repeat: 7 / 21

Let's proceed to step 6:
If we divide 7 by 21, we get 0 and a remainder of 7.
Put 0 as the next digit of the answer. 
Result so far: 6650.0
The remainder is 7 after subtracting 0 from 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

On to step 7:
21 can be fit into 70 3 times, resulting in a remainder of 7.
Write down 3 as next digit of the result. 
Result so far: 6650.3
If we take 63 away from 70, we end up with 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Going ahead to step 8:
The number 21 fits into 70 3 times, leaving a remainder of 7.
The next digit of our result is 3. 
Result so far: 6650.33
Subtract 63 from 70 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.

The final outcome is 6650.33, with a leftover of 0.007.