We look at the division of 394008 by 21 
We're looking to find how many times 21 goes into 394008.

Step 1:
The number 21 fits into 3 0 times, leaving a remainder of 3.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 3, we end up with 3.
Bring next digit (9) of the dividend behind the 3 and repeat the process: 39 / 21

Let's proceed to step 2:
When dividing 39 by 21, we get 1 with a remainder of 18.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
Subtracting 21 from 39 leaves us with 18.
Grab the next digit (4) from the dividend, add it to 18, then carry on: 184 / 21

Advancing to step 3:
21 goes into 184 8 times with a remainder of 16.
Put 8 as the next digit of the answer. 
Result so far: 18.0
Subtract 168 from 184 to get 16.
Grab the next digit (0) from the dividend, add it to 16, then carry on: 160 / 21

Let's proceed to step 4:
21 can be fit into 160 7 times, resulting in a remainder of 13.
The next digit of our result is 7. 
Result so far: 187.0
The remainder is 13 after subtracting 147 from 160.
Fetch the next digit (0) from the dividend, attach it to 13 and continue: 130 / 21

Step 5:
The number 21 fits into 130 6 times, leaving a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 1876.0
If we take 126 away from 130, we end up with 4.
Append the next digit (8) from the dividend to 4 and continue with: 48 / 21

Advancing to step 6:
48 divided by 21 is 2 with a remainder of 6.
The number 2 becomes the next digit in our result. 
Result so far: 18762.0
Deduct 42 from 48 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.

Let's proceed to step 7:
21 goes into 60 2 times with a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 18762.2
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.

Moving on to step 8:
When dividing 180 by 21, we get 8 with a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 18762.28
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.

Moving on to step 9:
If we divide 120 by 21, we get 5 and a remainder of 15.
The number 5 becomes the next digit in our result. 
Result so far: 18762.285
The remainder is 15 after subtracting 105 from 120.
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 10:
If we divide 150 by 21, we get 7 and a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 18762.2857
Subtracting 147 from 150 leaves us 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.

Step 11:
30 divided by 21 is 1 with a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 18762.28571
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.

On to step 12:
21 can be fit into 90 4 times, resulting in a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 18762.285714
Subtract 84 from 90 to 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.

Let's proceed to step 13:
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: 18762.2857142
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.

Advancing to step 14:
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: 18762.28571428
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.

After the division, we end up with 18762.28571428 and a remainder of 1.2e-08.