642648 ÷ 21 
Our goal is to divide 642648 by 21.

Going ahead to step 1:
6 divided by 21 is 0 with a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Grab the next digit (4) from the dividend, add it to 6, then carry on: 64 / 21

On to step 2:
21 can be fit into 64 3 times, resulting in a remainder of 1.
The number 3 becomes the next digit in our result. 
Result so far: 3.0
Subtract 63 from 64 to get 1.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 21

Moving on to step 3:
21 can be fit into 12 0 times, resulting in a remainder of 12.
Record the quotient 0 as the next digit in the result. 
Result so far: 30.0
Subtract 0 from 12 to get 12.
Include the next digit (6) from the dividend after 12, then repeat: 126 / 21

Moving on to step 4:
21 can be fit into 126 6 times, resulting in a remainder of 0.
Use 6 as the next digit of our solution. 
Result so far: 306.0
Subtracting 126 from 126 leaves us with 0.
Grab the next digit (4) from the dividend, add it to 0, then carry on: 4 / 21

Going ahead to step 5:
21 can be fit into 4 0 times, resulting in a remainder of 4.
Write down 0 as next digit of the result. 
Result so far: 3060.0
If we subtract 0 from 4, we get 4.
Grab the next digit (8) from the dividend, add it to 4, then carry on: 48 / 21

Moving on to step 6:
The number 21 fits into 48 2 times, leaving a remainder of 6.
The number 2 becomes the next digit in our result. 
Result so far: 30602.0
If we subtract 42 from 48, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 7:
The number 21 fits into 60 2 times, leaving a remainder of 18.
The number 2 becomes the next digit in our result. 
Result so far: 30602.2
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 8:
If we divide 180 by 21, we get 8 and a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 30602.28
Subtracting 168 from 180 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Going ahead to step 9:
21 goes into 120 5 times with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 30602.285
Subtract 105 from 120 to get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Let's proceed to step 10:
If we divide 150 by 21, we get 7 and a remainder of 3.
Write down 7 as next digit of the result. 
Result so far: 30602.2857
If we take 147 away from 150, we end up 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.

Advancing to step 11:
21 goes into 30 1 times with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 30602.28571
Deduct 21 from 30 and we're left with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 12:
The number 21 fits into 90 4 times, leaving a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 30602.285714
Deduct 84 from 90 and we're left with 6.
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 13:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 30602.2857142
Subtracting 42 from 60 leaves us 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 14:
180 divided by 21 is 8 with a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 30602.28571428
Deduct 168 from 180 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

The quotient of the division is 30602.28571428, and the remainder is 1.2e-08.