We divide 215866 by 21
Let's see how many times 21 fits into 215866.

Advancing to step 1:
When dividing 2 by 21, we get 0 with a remainder of 2.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 2 leaves us with 2.
Include the next digit (1) from the dividend after 2, then repeat: 21 / 21

Going ahead to step 2:
The number 21 fits into 21 1 times, leaving a remainder of 0.
The next digit of our result is 1. 
Result so far: 1.0
Subtracting 21 from 21 leaves us with 0.
Include the next digit (5) from the dividend after 0, then repeat: 5 / 21

Going ahead to step 3:
The number 21 fits into 5 0 times, leaving a remainder of 5.
Record the quotient 0 as the next digit in the result. 
Result so far: 10.0
Subtract 0 from 5 to get 5.
Append the next digit (8) from the dividend to 5 and continue with: 58 / 21

Let's proceed to step 4:
If we divide 58 by 21, we get 2 and a remainder of 16.
The next digit of our result is 2. 
Result so far: 102.0
Subtracting 42 from 58 leaves us with 16.
Fetch the next digit (6) from the dividend, attach it to 16 and continue: 166 / 21

Advancing to step 5:
The number 21 fits into 166 7 times, leaving a remainder of 19.
Use 7 as the next digit of our solution. 
Result so far: 1027.0
If we subtract 147 from 166, we get 19.
Take the next digit (6) from the dividend and append it to 19, then repeat: 196 / 21

Going ahead to step 6:
21 can be fit into 196 9 times, resulting in a remainder of 7.
Write down 9 as next digit of the result. 
Result so far: 10279.0
Subtracting 189 from 196 leaves us with 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

On to step 7:
70 divided by 21 is 3 with a remainder of 7.
The number 3 becomes the next digit in our result. 
Result so far: 10279.3
Deduct 63 from 70 and we're left with 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Going ahead to step 8:
When dividing 70 by 21, we get 3 with a remainder of 7.
The next digit of our result is 3. 
Result so far: 10279.33
Subtract 63 from 70 to get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

The final outcome is 10279.33, with a leftover of 0.007.