We look at the division of 638579 by 21 
Our goal is to divide 638579 by 21.

Let's proceed to step 1:
The number 21 fits into 6 0 times, leaving a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 6 to get 6.
Grab the next digit (3) from the dividend, add it to 6, then carry on: 63 / 21

Moving on to step 2:
If we divide 63 by 21, we get 3 and a remainder of 0.
The next digit of our result is 3. 
Result so far: 3.0
Deduct 63 from 63 and we're left with 0.
Grab the next digit (8) from the dividend, add it to 0, then carry on: 8 / 21

Step 3:
21 goes into 8 0 times with a remainder of 8.
The number 0 becomes the next digit in our result. 
Result so far: 30.0
Subtract 0 from 8 to get 8.
Bring next digit (5) of the dividend behind the 8 and repeat the process: 85 / 21

Going ahead to step 4:
When dividing 85 by 21, we get 4 with a remainder of 1.
Record the quotient 4 as the next digit in the result. 
Result so far: 304.0
Subtracting 84 from 85 leaves us with 1.
Fetch the next digit (7) from the dividend, attach it to 1 and continue: 17 / 21

Going ahead to step 5:
The number 21 fits into 17 0 times, leaving a remainder of 17.
The next digit of our result is 0. 
Result so far: 3040.0
Subtracting 0 from 17 leaves us with 17.
Take the next digit (9) from the dividend and append it to 17, then repeat: 179 / 21

Going ahead to step 6:
When dividing 179 by 21, we get 8 with a remainder of 11.
Use 8 as the next digit of our solution. 
Result so far: 30408.0
Subtracting 168 from 179 leaves us with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Moving on to step 7:
110 divided by 21 is 5 with a remainder of 5.
Write down 5 as next digit of the result. 
Result so far: 30408.5
If we subtract 105 from 110, we get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Step 8:
The number 21 fits into 50 2 times, leaving a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 30408.52
If we take 42 away from 50, we end up with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 9:
21 goes into 80 3 times with a remainder of 17.
Put 3 as the next digit of the answer. 
Result so far: 30408.523
Subtracting 63 from 80 leaves us with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Step 10:
The number 21 fits into 170 8 times, leaving a remainder of 2.
The number 8 becomes the next digit in our result. 
Result so far: 30408.5238
Deduct 168 from 170 and we're left with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 11:
21 goes into 20 0 times with a remainder of 20.
Write down 0 as next digit of the result. 
Result so far: 30408.5238
Subtract 0 from 20 to get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

On to step 12:
When dividing 200 by 21, we get 9 with a remainder of 11.
Record the quotient 9 as the next digit in the result. 
Result so far: 30408.523809
If we subtract 189 from 200, we get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Let's proceed to step 13:
When dividing 110 by 21, we get 5 with a remainder of 5.
Use 5 as the next digit of our solution. 
Result so far: 30408.5238095
If we take 105 away from 110, we end up with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Moving on to step 14:
The number 21 fits into 50 2 times, leaving a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 30408.52380952
Deduct 42 from 50 and we're left with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

In conclusion, the division gives 30408.52380952 with a balance of 8e-09.