We're dividing 408069 by 21 
We want to divide 408069 by 21.

Step 1:
The number 21 fits into 4 0 times, leaving a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 4 to get 4.
Take the next digit (0) from the dividend and append it to 4, then repeat: 40 / 21

Moving on to step 2:
When dividing 40 by 21, we get 1 with a remainder of 19.
The next digit of our result is 1. 
Result so far: 1.0
If we subtract 21 from 40, we get 19.
Bring next digit (8) of the dividend behind the 19 and repeat the process: 198 / 21

Moving on to step 3:
21 can be fit into 198 9 times, resulting in a remainder of 9.
Record the quotient 9 as the next digit in the result. 
Result so far: 19.0
The remainder is 9 after subtracting 189 from 198.
Bring next digit (0) of the dividend behind the 9 and repeat the process: 90 / 21

Let's proceed to step 4:
If we divide 90 by 21, we get 4 and a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 194.0
Subtracting 84 from 90 leaves us with 6.
Take the next digit (6) from the dividend and append it to 6, then repeat: 66 / 21

On to step 5:
When dividing 66 by 21, we get 3 with a remainder of 3.
Record the quotient 3 as the next digit in the result. 
Result so far: 1943.0
Deduct 63 from 66 and we're left with 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 21

On to step 6:
21 goes into 39 1 times with a remainder of 18.
Put 1 as the next digit of the answer. 
Result so far: 19431.0
Subtract 21 from 39 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.

Let's proceed to step 7:
21 goes into 180 8 times with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 19431.8
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.

Moving on to step 8:
21 can be fit into 120 5 times, resulting in a remainder of 15.
The number 5 becomes the next digit in our result. 
Result so far: 19431.85
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.

Advancing to step 9:
The number 21 fits into 150 7 times, leaving a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 19431.857
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.

Moving on to step 10:
30 divided by 21 is 1 with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 19431.8571
Deduct 21 from 30 and we're left 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.

On to step 11:
90 divided by 21 is 4 with a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 19431.85714
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.

Let's proceed to step 12:
When dividing 60 by 21, we get 2 with a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 19431.857142
If we subtract 42 from 60, 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.

Advancing to step 13:
When dividing 180 by 21, we get 8 with a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 19431.8571428
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:
21 can be fit into 120 5 times, resulting in a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 19431.85714285
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.

In conclusion, the division gives 19431.85714285 with a balance of 1.5e-08.