21084120 ÷ 81 
We want to figure out the number of times 21084120 can be divided by 81.

Moving on to step 1:
When dividing 2 by 81, we get 0 with a remainder of 2.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 2 after subtracting 0 from 2.
Include the next digit (1) from the dividend after 2, then repeat: 21 / 81

Moving on to step 2:
21 divided by 81 is 0 with a remainder of 21.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 21 after subtracting 0 from 21.
Include the next digit (0) from the dividend after 21, then repeat: 210 / 81

Moving on to step 3:
When dividing 210 by 81, we get 2 with a remainder of 48.
Write down 2 as next digit of the result. 
Result so far: 2.0
If we take 162 away from 210, we end up with 48.
Grab the next digit (8) from the dividend, add it to 48, then carry on: 488 / 81

Step 4:
If we divide 488 by 81, we get 6 and a remainder of 2.
Put 6 as the next digit of the answer. 
Result so far: 26.0
Subtract 486 from 488 to get 2.
Bring next digit (4) of the dividend behind the 2 and repeat the process: 24 / 81

Advancing to step 5:
81 goes into 24 0 times with a remainder of 24.
Write down 0 as next digit of the result. 
Result so far: 260.0
Subtract 0 from 24 to get 24.
Fetch the next digit (1) from the dividend, attach it to 24 and continue: 241 / 81

Going ahead to step 6:
The number 81 fits into 241 2 times, leaving a remainder of 79.
The number 2 becomes the next digit in our result. 
Result so far: 2602.0
Subtract 162 from 241 to get 79.
Fetch the next digit (2) from the dividend, attach it to 79 and continue: 792 / 81

Let's proceed to step 7:
81 goes into 792 9 times with a remainder of 63.
Use 9 as the next digit of our solution. 
Result so far: 26029.0
Subtracting 729 from 792 leaves us with 63.
Take the next digit (0) from the dividend and append it to 63, then repeat: 630 / 81

Moving on to step 8:
When dividing 630 by 81, we get 7 with a remainder of 63.
Write down 7 as next digit of the result. 
Result so far: 260297.0
If we take 567 away from 630, we end up with 63.
Since there are no more digits in the dividend, we add a zero to the remainder making it 630, and continue the process.

Moving on to step 9:
630 divided by 81 is 7 with a remainder of 63.
Record the quotient 7 as the next digit in the result. 
Result so far: 260297.7
Subtract 567 from 630 to get 63.
Since there are no more digits in the dividend, we add a zero to the remainder making it 630, and continue the process.

Advancing to step 10:
630 divided by 81 is 7 with a remainder of 63.
The next digit of our result is 7. 
Result so far: 260297.77
Deduct 567 from 630 and we're left with 63.
Since there are no more digits in the dividend, we add a zero to the remainder making it 630, and continue the process.

After the division, we end up with 260297.77 and a remainder of 0.063.