21635839 divided by 720 
We want to figure out the number of times 21635839 can be divided by 720.

Going ahead to step 1:
When dividing 2 by 720, we get 0 with a remainder of 2.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 2 leaves us with 2.
Take the next digit (1) from the dividend and append it to 2, then repeat: 21 / 720

On to step 2:
720 can be fit into 21 0 times, resulting in a remainder of 21.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 21, we end up with 21.
Take the next digit (6) from the dividend and append it to 21, then repeat: 216 / 720

Advancing to step 3:
216 divided by 720 is 0 with a remainder of 216.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 216 leaves us with 216.
Fetch the next digit (3) from the dividend, attach it to 216 and continue: 2163 / 720

Let's proceed to step 4:
The number 720 fits into 2163 3 times, leaving a remainder of 3.
The next digit of our result is 3. 
Result so far: 3.0
If we take 2160 away from 2163, we end up with 3.
Append the next digit (5) from the dividend to 3 and continue with: 35 / 720

Let's proceed to step 5:
720 goes into 35 0 times with a remainder of 35.
The number 0 becomes the next digit in our result. 
Result so far: 30.0
The remainder is 35 after subtracting 0 from 35.
Take the next digit (8) from the dividend and append it to 35, then repeat: 358 / 720

Let's proceed to step 6:
The number 720 fits into 358 0 times, leaving a remainder of 358.
Write down 0 as next digit of the result. 
Result so far: 300.0
If we subtract 0 from 358, we get 358.
Grab the next digit (3) from the dividend, add it to 358, then carry on: 3583 / 720

Advancing to step 7:
The number 720 fits into 3583 4 times, leaving a remainder of 703.
Write down 4 as next digit of the result. 
Result so far: 3004.0
Subtract 2880 from 3583 to get 703.
Take the next digit (9) from the dividend and append it to 703, then repeat: 7039 / 720

Going ahead to step 8:
720 can be fit into 7039 9 times, resulting in a remainder of 559.
Put 9 as the next digit of the answer. 
Result so far: 30049.0
If we take 6480 away from 7039, we end up with 559.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5590, and continue the process.

Moving on to step 9:
If we divide 5590 by 720, we get 7 and a remainder of 550.
Write down 7 as next digit of the result. 
Result so far: 30049.7
Deduct 5040 from 5590 and we're left with 550.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5500, and continue the process.

Advancing to step 10:
720 can be fit into 5500 7 times, resulting in a remainder of 460.
Put 7 as the next digit of the answer. 
Result so far: 30049.77
If we take 5040 away from 5500, we end up with 460.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4600, and continue the process.

The final outcome is 30049.77, with a leftover of 0.46.