3980352 ÷ 21 
We're looking to find how many times 21 goes into 3980352.

Advancing to step 1:
21 can be fit into 3 0 times, resulting in a remainder of 3.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 3, we get 3.
Grab the next digit (9) from the dividend, add it to 3, then carry on: 39 / 21

Going ahead to step 2:
21 goes into 39 1 times with a remainder of 18.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
Subtract 21 from 39 to get 18.
Fetch the next digit (8) from the dividend, attach it to 18 and continue: 188 / 21

Moving on to step 3:
21 goes into 188 8 times with a remainder of 20.
Use 8 as the next digit of our solution. 
Result so far: 18.0
The remainder is 20 after subtracting 168 from 188.
Include the next digit (0) from the dividend after 20, then repeat: 200 / 21

On to step 4:
When dividing 200 by 21, we get 9 with a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 189.0
The remainder is 11 after subtracting 189 from 200.
Grab the next digit (3) from the dividend, add it to 11, then carry on: 113 / 21

Moving on to step 5:
21 goes into 113 5 times with a remainder of 8.
The number 5 becomes the next digit in our result. 
Result so far: 1895.0
Deduct 105 from 113 and we're left with 8.
Append the next digit (5) from the dividend to 8 and continue with: 85 / 21

On to step 6:
85 divided by 21 is 4 with a remainder of 1.
The number 4 becomes the next digit in our result. 
Result so far: 18954.0
Deduct 84 from 85 and we're left with 1.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 21

On to step 7:
12 divided by 21 is 0 with a remainder of 12.
Put 0 as the next digit of the answer. 
Result so far: 189540.0
The remainder is 12 after subtracting 0 from 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 8:
21 can be fit into 120 5 times, resulting in a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 189540.5
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:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 189540.57
Deduct 147 from 150 and we're left 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.

On to step 10:
The number 21 fits into 30 1 times, leaving a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 189540.571
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.

Step 11:
If we divide 90 by 21, we get 4 and a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 189540.5714
Subtracting 84 from 90 leaves us 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.

Going ahead to step 12:
60 divided by 21 is 2 with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 189540.57142
If we take 42 away from 60, we end up with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Going ahead to step 13:
180 divided by 21 is 8 with a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 189540.571428
If we subtract 168 from 180, we 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.

Moving on to step 14:
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: 189540.5714285
If we take 105 away from 120, we end up 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.

Advancing to step 15:
21 can be fit into 150 7 times, resulting in a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 189540.57142857
If we take 147 away from 150, we end up 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.

In conclusion, the division gives 189540.57142857 with a balance of 3e-09.