288720 ÷ 21 
We're looking to find how many times 21 goes into 288720.

Step 1:
21 can be fit into 2 0 times, resulting in a remainder of 2.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 2, we end up with 2.
Bring next digit (8) of the dividend behind the 2 and repeat the process: 28 / 21

Moving on to step 2:
When dividing 28 by 21, we get 1 with a remainder of 7.
Use 1 as the next digit of our solution. 
Result so far: 1.0
If we subtract 21 from 28, we get 7.
Bring next digit (8) of the dividend behind the 7 and repeat the process: 78 / 21

Advancing to step 3:
If we divide 78 by 21, we get 3 and a remainder of 15.
Record the quotient 3 as the next digit in the result. 
Result so far: 13.0
The remainder is 15 after subtracting 63 from 78.
Bring next digit (7) of the dividend behind the 15 and repeat the process: 157 / 21

Step 4:
If we divide 157 by 21, we get 7 and a remainder of 10.
Put 7 as the next digit of the answer. 
Result so far: 137.0
Subtract 147 from 157 to get 10.
Take the next digit (2) from the dividend and append it to 10, then repeat: 102 / 21

Let's proceed to step 5:
The number 21 fits into 102 4 times, leaving a remainder of 18.
The number 4 becomes the next digit in our result. 
Result so far: 1374.0
If we subtract 84 from 102, we get 18.
Bring next digit (0) of the dividend behind the 18 and repeat the process: 180 / 21

Let's proceed to step 6:
21 can be fit into 180 8 times, resulting in a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 13748.0
Subtract 168 from 180 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Moving on to step 7:
When dividing 120 by 21, we get 5 with a remainder of 15.
The number 5 becomes the next digit in our result. 
Result so far: 13748.5
If we take 105 away from 120, we end up with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Advancing to step 8:
When dividing 150 by 21, we get 7 with a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 13748.57
The remainder is 3 after subtracting 147 from 150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Moving on to step 9:
21 goes into 30 1 times with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 13748.571
The remainder is 9 after subtracting 21 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Advancing to step 10:
21 goes into 90 4 times with a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 13748.5714
The remainder is 6 after subtracting 84 from 90.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Moving on to step 11:
21 can be fit into 60 2 times, resulting in a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 13748.57142
Deduct 42 from 60 and we're left with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Step 12:
21 goes into 180 8 times with a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 13748.571428
The remainder is 12 after subtracting 168 from 180.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Moving on to step 13:
21 can be fit into 120 5 times, resulting in a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 13748.5714285
If we take 105 away from 120, we end up with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Advancing to step 14:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 13748.57142857
Deduct 147 from 150 and we're left with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

The quotient of the division is 13748.57142857, and the remainder is 3e-09.