638397 divided by 21 
Let's see how many times 21 fits into 638397.

Let's proceed to step 1:
If we divide 6 by 21, we get 0 and a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Fetch the next digit (3) from the dividend, attach it to 6 and continue: 63 / 21

Let's proceed to step 2:
21 goes into 63 3 times with a remainder of 0.
Write down 3 as next digit of the result. 
Result so far: 3.0
If we subtract 63 from 63, we get 0.
Fetch the next digit (8) from the dividend, attach it to 0 and continue: 8 / 21

Step 3:
The number 21 fits into 8 0 times, leaving a remainder of 8.
The next digit of our result is 0. 
Result so far: 30.0
Subtracting 0 from 8 leaves us with 8.
Append the next digit (3) from the dividend to 8 and continue with: 83 / 21

Let's proceed to step 4:
21 goes into 83 3 times with a remainder of 20.
Put 3 as the next digit of the answer. 
Result so far: 303.0
If we subtract 63 from 83, we get 20.
Take the next digit (9) from the dividend and append it to 20, then repeat: 209 / 21

Advancing to step 5:
If we divide 209 by 21, we get 9 and a remainder of 20.
Put 9 as the next digit of the answer. 
Result so far: 3039.0
If we subtract 189 from 209, we get 20.
Include the next digit (7) from the dividend after 20, then repeat: 207 / 21

Moving on to step 6:
The number 21 fits into 207 9 times, leaving a remainder of 18.
Use 9 as the next digit of our solution. 
Result so far: 30399.0
If we subtract 189 from 207, we get 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 7:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 30399.8
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.

Advancing to step 8:
120 divided by 21 is 5 with a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 30399.85
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.

On to step 9:
If we divide 150 by 21, we get 7 and a remainder of 3.
The next digit of our result is 7. 
Result so far: 30399.857
If we subtract 147 from 150, we 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.

Going ahead to step 10:
If we divide 30 by 21, we get 1 and a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 30399.8571
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.

Moving on to step 11:
90 divided by 21 is 4 with a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 30399.85714
Deduct 84 from 90 and we're left 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 12:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 30399.857142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Advancing to step 13:
When dividing 180 by 21, we get 8 with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 30399.8571428
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.

Going ahead to step 14:
21 goes into 120 5 times with a remainder of 15.
The next digit of our result is 5. 
Result so far: 30399.85714285
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.

Our division results in 30399.85714285 with a remaining 1.5e-08.