125868 ÷ 21 
Our goal is to divide 125868 by 21.

Step 1:
If we divide 1 by 21, we get 0 and a remainder of 1.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 1 leaves us with 1.
Take the next digit (2) from the dividend and append it to 1, then repeat: 12 / 21

On to step 2:
12 divided by 21 is 0 with a remainder of 12.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 12, we get 12.
Append the next digit (5) from the dividend to 12 and continue with: 125 / 21

Going ahead to step 3:
The number 21 fits into 125 5 times, leaving a remainder of 20.
Write down 5 as next digit of the result. 
Result so far: 5.0
If we subtract 105 from 125, we get 20.
Fetch the next digit (8) from the dividend, attach it to 20 and continue: 208 / 21

Step 4:
When dividing 208 by 21, we get 9 with a remainder of 19.
The number 9 becomes the next digit in our result. 
Result so far: 59.0
If we subtract 189 from 208, we get 19.
Take the next digit (6) from the dividend and append it to 19, then repeat: 196 / 21

Moving on to step 5:
196 divided by 21 is 9 with a remainder of 7.
Write down 9 as next digit of the result. 
Result so far: 599.0
Deduct 189 from 196 and we're left with 7.
Grab the next digit (8) from the dividend, add it to 7, then carry on: 78 / 21

Let's proceed to step 6:
78 divided by 21 is 3 with a remainder of 15.
Put 3 as the next digit of the answer. 
Result so far: 5993.0
Subtract 63 from 78 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.

Moving on to step 7:
When dividing 150 by 21, we get 7 with a remainder of 3.
The next digit of our result is 7. 
Result so far: 5993.7
Subtract 147 from 150 to 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.

Advancing to step 8:
21 goes into 30 1 times with a remainder of 9.
The number 1 becomes the next digit in our result. 
Result so far: 5993.71
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 9:
21 goes into 90 4 times with a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 5993.714
If we subtract 84 from 90, we get 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 10:
If we divide 60 by 21, we get 2 and a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 5993.7142
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 11:
If we divide 180 by 21, we get 8 and a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 5993.71428
Subtracting 168 from 180 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Going ahead to step 12:
If we divide 120 by 21, we get 5 and a remainder of 15.
The next digit of our result is 5. 
Result so far: 5993.714285
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.

Moving on to step 13:
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: 5993.7142857
The remainder is 3 after subtracting 147 from 150.
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 14:
The number 21 fits into 30 1 times, leaving a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 5993.71428571
Subtract 21 from 30 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.

The final result is 5993.71428571 with a remainder of 9e-09.