We look at the division of 354069 by 21 
We want to figure out the number of times 354069 can be divided by 21.

Going ahead to step 1:
21 can be fit into 3 0 times, resulting in a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Grab the next digit (5) from the dividend, add it to 3, then carry on: 35 / 21

Moving on to step 2:
21 can be fit into 35 1 times, resulting in a remainder of 14.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
Subtracting 21 from 35 leaves us with 14.
Fetch the next digit (4) from the dividend, attach it to 14 and continue: 144 / 21

Going ahead to step 3:
If we divide 144 by 21, we get 6 and a remainder of 18.
Write down 6 as next digit of the result. 
Result so far: 16.0
If we subtract 126 from 144, we get 18.
Take the next digit (0) from the dividend and append it to 18, then repeat: 180 / 21

Going ahead to step 4:
21 goes into 180 8 times with a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 168.0
Deduct 168 from 180 and we're left with 12.
Append the next digit (6) from the dividend to 12 and continue with: 126 / 21

Moving on to step 5:
When dividing 126 by 21, we get 6 with a remainder of 0.
Write down 6 as next digit of the result. 
Result so far: 1686.0
If we subtract 126 from 126, we get 0.
Append the next digit (9) from the dividend to 0 and continue with: 9 / 21

On to step 6:
When dividing 9 by 21, we get 0 with a remainder of 9.
Put 0 as the next digit of the answer. 
Result so far: 16860.0
Subtract 0 from 9 to 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.

Let's proceed to step 7:
The number 21 fits into 90 4 times, leaving a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 16860.4
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 8:
21 goes into 60 2 times with a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 16860.42
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.

Going ahead to step 9:
The number 21 fits into 180 8 times, leaving a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 16860.428
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.

On to step 10:
21 goes into 120 5 times with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 16860.4285
Subtract 105 from 120 to get 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 11:
21 goes into 150 7 times with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 16860.42857
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.

Let's proceed to step 12:
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: 16860.428571
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.

Moving on to step 13:
90 divided by 21 is 4 with a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 16860.4285714
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.

On to step 14:
The number 21 fits into 60 2 times, leaving a remainder of 18.
The number 2 becomes the next digit in our result. 
Result so far: 16860.42857142
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.

In conclusion, the division gives 16860.42857142 with a balance of 1.8e-08.