21086512 ÷ 8 
Let's see how many times 8 fits into 21086512.

Let's proceed to step 1:
When dividing 2 by 8, we get 0 with a remainder of 2.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 2 to get 2.
Append the next digit (1) from the dividend to 2 and continue with: 21 / 8

Step 2:
The number 8 fits into 21 2 times, leaving a remainder of 5.
The next digit of our result is 2. 
Result so far: 2.0
The remainder is 5 after subtracting 16 from 21.
Include the next digit (0) from the dividend after 5, then repeat: 50 / 8

Moving on to step 3:
When dividing 50 by 8, we get 6 with a remainder of 2.
Record the quotient 6 as the next digit in the result. 
Result so far: 26.0
Subtract 48 from 50 to get 2.
Take the next digit (8) from the dividend and append it to 2, then repeat: 28 / 8

On to step 4:
8 can be fit into 28 3 times, resulting in a remainder of 4.
Record the quotient 3 as the next digit in the result. 
Result so far: 263.0
Subtracting 24 from 28 leaves us with 4.
Bring next digit (6) of the dividend behind the 4 and repeat the process: 46 / 8

Step 5:
The number 8 fits into 46 5 times, leaving a remainder of 6.
The next digit of our result is 5. 
Result so far: 2635.0
Deduct 40 from 46 and we're left with 6.
Grab the next digit (5) from the dividend, add it to 6, then carry on: 65 / 8

Step 6:
When dividing 65 by 8, we get 8 with a remainder of 1.
The next digit of our result is 8. 
Result so far: 26358.0
Subtracting 64 from 65 leaves us with 1.
Include the next digit (1) from the dividend after 1, then repeat: 11 / 8

Going ahead to step 7:
If we divide 11 by 8, we get 1 and a remainder of 3.
Put 1 as the next digit of the answer. 
Result so far: 263581.0
If we take 8 away from 11, we end up with 3.
Fetch the next digit (2) from the dividend, attach it to 3 and continue: 32 / 8

On to step 8:
If we divide 32 by 8, we get 4 and a remainder of 0.
Put 4 as the next digit of the answer. 
Result so far: 2635814.0
If we subtract 32 from 32, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Moving on to step 9:
0 divided by 8 is 0 with a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 2635814.0
If we take 0 away from 0, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Going ahead to step 10:
When dividing 0 by 8, we get 0 with a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 2635814.0
Deduct 0 from 0 and we're left with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

After the division, we end up with 2635814.0 and a remainder of 0.0.