300720 divided by 21 
Let's see how many times 21 fits into 300720.

Step 1:
When dividing 3 by 21, we get 0 with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Grab the next digit (0) from the dividend, add it to 3, then carry on: 30 / 21

Advancing to step 2:
21 goes into 30 1 times with a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
Subtract 21 from 30 to get 9.
Include the next digit (0) from the dividend after 9, then repeat: 90 / 21

Moving on to step 3:
21 can be fit into 90 4 times, resulting in a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 14.0
Subtract 84 from 90 to get 6.
Bring next digit (7) of the dividend behind the 6 and repeat the process: 67 / 21

Advancing to step 4:
When dividing 67 by 21, we get 3 with a remainder of 4.
The number 3 becomes the next digit in our result. 
Result so far: 143.0
Deduct 63 from 67 and we're left with 4.
Bring next digit (2) of the dividend behind the 4 and repeat the process: 42 / 21

Moving on to step 5:
42 divided by 21 is 2 with a remainder of 0.
Use 2 as the next digit of our solution. 
Result so far: 1432.0
If we subtract 42 from 42, we get 0.
Grab the next digit (0) from the dividend, add it to 0, then carry on: 0 / 21

Going ahead to step 6:
21 goes into 0 0 times with a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 14320.0
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.

Let's proceed to step 7:
The number 21 fits into 0 0 times, leaving a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 14320.0
Subtracting 0 from 0 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.

Moving on to step 8:
If we divide 0 by 21, we get 0 and a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 14320.0
Subtracting 0 from 0 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.

The final outcome is 14320.0, with a leftover of 0.0.