81952878 ÷ 21 
We want to figure out the number of times 81952878 can be divided by 21.

Step 1:
If we divide 8 by 21, we get 0 and a remainder of 8.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 8 to get 8.
Fetch the next digit (1) from the dividend, attach it to 8 and continue: 81 / 21

Moving on to step 2:
The number 21 fits into 81 3 times, leaving a remainder of 18.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
If we subtract 63 from 81, we get 18.
Bring next digit (9) of the dividend behind the 18 and repeat the process: 189 / 21

Moving on to step 3:
21 can be fit into 189 9 times, resulting in a remainder of 0.
The next digit of our result is 9. 
Result so far: 39.0
Deduct 189 from 189 and we're left with 0.
Bring next digit (5) of the dividend behind the 0 and repeat the process: 5 / 21

Moving on to step 4:
21 can be fit into 5 0 times, resulting in a remainder of 5.
Record the quotient 0 as the next digit in the result. 
Result so far: 390.0
If we subtract 0 from 5, we get 5.
Fetch the next digit (2) from the dividend, attach it to 5 and continue: 52 / 21

Advancing to step 5:
21 can be fit into 52 2 times, resulting in a remainder of 10.
The next digit of our result is 2. 
Result so far: 3902.0
Subtracting 42 from 52 leaves us with 10.
Fetch the next digit (8) from the dividend, attach it to 10 and continue: 108 / 21

Going ahead to step 6:
21 can be fit into 108 5 times, resulting in a remainder of 3.
The number 5 becomes the next digit in our result. 
Result so far: 39025.0
If we take 105 away from 108, we end up with 3.
Grab the next digit (7) from the dividend, add it to 3, then carry on: 37 / 21

Advancing to step 7:
When dividing 37 by 21, we get 1 with a remainder of 16.
Use 1 as the next digit of our solution. 
Result so far: 390251.0
The remainder is 16 after subtracting 21 from 37.
Include the next digit (8) from the dividend after 16, then repeat: 168 / 21

Step 8:
The number 21 fits into 168 8 times, leaving a remainder of 0.
The next digit of our result is 8. 
Result so far: 3902518.0
Subtracting 168 from 168 leaves us 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.

Advancing to step 9:
The number 21 fits into 0 0 times, leaving a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 3902518.0
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.

On to step 10:
When dividing 0 by 21, we get 0 with a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 3902518.0
Subtract 0 from 0 to 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.

The final outcome is 3902518.0, with a leftover of 0.0.