243857 ÷ 21 
We're looking to find how many times 21 goes into 243857.

Let's proceed to step 1:
21 goes into 2 0 times with a remainder of 2.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 2 to get 2.
Fetch the next digit (4) from the dividend, attach it to 2 and continue: 24 / 21

Let's proceed to step 2:
21 goes into 24 1 times with a remainder of 3.
Write down 1 as next digit of the result. 
Result so far: 1.0
If we take 21 away from 24, we end up with 3.
Grab the next digit (3) from the dividend, add it to 3, then carry on: 33 / 21

Moving on to step 3:
The number 21 fits into 33 1 times, leaving a remainder of 12.
Use 1 as the next digit of our solution. 
Result so far: 11.0
If we subtract 21 from 33, we get 12.
Grab the next digit (8) from the dividend, add it to 12, then carry on: 128 / 21

Going ahead to step 4:
128 divided by 21 is 6 with a remainder of 2.
The next digit of our result is 6. 
Result so far: 116.0
Subtract 126 from 128 to get 2.
Include the next digit (5) from the dividend after 2, then repeat: 25 / 21

Step 5:
25 divided by 21 is 1 with a remainder of 4.
The number 1 becomes the next digit in our result. 
Result so far: 1161.0
If we take 21 away from 25, we end up with 4.
Grab the next digit (7) from the dividend, add it to 4, then carry on: 47 / 21

On to step 6:
21 can be fit into 47 2 times, resulting in a remainder of 5.
Put 2 as the next digit of the answer. 
Result so far: 11612.0
Subtracting 42 from 47 leaves us with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Going ahead to step 7:
50 divided by 21 is 2 with a remainder of 8.
The number 2 becomes the next digit in our result. 
Result so far: 11612.2
Subtracting 42 from 50 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 8:
21 goes into 80 3 times with a remainder of 17.
Put 3 as the next digit of the answer. 
Result so far: 11612.23
If we take 63 away from 80, we end up with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

On to step 9:
If we divide 170 by 21, we get 8 and a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 11612.238
The remainder is 2 after subtracting 168 from 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Advancing to step 10:
If we divide 20 by 21, we get 0 and a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 11612.238
Subtracting 0 from 20 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 11:
21 goes into 200 9 times with a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 11612.23809
Deduct 189 from 200 and we're left with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Going ahead to step 12:
21 can be fit into 110 5 times, resulting in a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 11612.238095
If we subtract 105 from 110, we get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Advancing to step 13:
When dividing 50 by 21, we get 2 with a remainder of 8.
The next digit of our result is 2. 
Result so far: 11612.2380952
Subtract 42 from 50 to get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Step 14:
When dividing 80 by 21, we get 3 with a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 11612.23809523
Subtracting 63 from 80 leaves us with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

In conclusion, the division gives 11612.23809523 with a balance of 1.7e-08.