We look at the division of 393241 by 21 
We're looking to find how many times 21 goes into 393241.

On to step 1:
If we divide 3 by 21, we get 0 and a remainder of 3.
The next digit of our result is 0. 
Result so far: 0.0
The remainder is 3 after subtracting 0 from 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 21

Let's proceed to step 2:
39 divided by 21 is 1 with a remainder of 18.
Put 1 as the next digit of the answer. 
Result so far: 1.0
The remainder is 18 after subtracting 21 from 39.
Grab the next digit (3) from the dividend, add it to 18, then carry on: 183 / 21

On to step 3:
21 can be fit into 183 8 times, resulting in a remainder of 15.
Record the quotient 8 as the next digit in the result. 
Result so far: 18.0
If we subtract 168 from 183, we get 15.
Include the next digit (2) from the dividend after 15, then repeat: 152 / 21

Advancing to step 4:
152 divided by 21 is 7 with a remainder of 5.
Use 7 as the next digit of our solution. 
Result so far: 187.0
Subtracting 147 from 152 leaves us with 5.
Bring next digit (4) of the dividend behind the 5 and repeat the process: 54 / 21

On to step 5:
If we divide 54 by 21, we get 2 and a remainder of 12.
Use 2 as the next digit of our solution. 
Result so far: 1872.0
If we take 42 away from 54, we end up with 12.
Append the next digit (1) from the dividend to 12 and continue with: 121 / 21

Going ahead to step 6:
121 divided by 21 is 5 with a remainder of 16.
Use 5 as the next digit of our solution. 
Result so far: 18725.0
If we take 105 away from 121, we end up with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Going ahead to step 7:
21 can be fit into 160 7 times, resulting in a remainder of 13.
Put 7 as the next digit of the answer. 
Result so far: 18725.7
The remainder is 13 after subtracting 147 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 8:
When dividing 130 by 21, we get 6 with a remainder of 4.
The next digit of our result is 6. 
Result so far: 18725.76
If we subtract 126 from 130, we get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 9:
21 goes into 40 1 times with a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 18725.761
Deduct 21 from 40 and we're left with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 10:
If we divide 190 by 21, we get 9 and a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 18725.7619
If we take 189 away from 190, we end up with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Going ahead to step 11:
When dividing 10 by 21, we get 0 with a remainder of 10.
Use 0 as the next digit of our solution. 
Result so far: 18725.7619
Deduct 0 from 10 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Advancing to step 12:
When dividing 100 by 21, we get 4 with a remainder of 16.
Record the quotient 4 as the next digit in the result. 
Result so far: 18725.761904
If we take 84 away from 100, we end up with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Moving on to step 13:
160 divided by 21 is 7 with a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 18725.7619047
If we subtract 147 from 160, we get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Moving on to step 14:
21 goes into 130 6 times with a remainder of 4.
Record the quotient 6 as the next digit in the result. 
Result so far: 18725.76190476
If we take 126 away from 130, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

In conclusion, the division gives 18725.76190476 with a balance of 4e-09.