We're dividing 673391 by 21 
We want to figure out the number of times 673391 can be divided by 21.

Step 1:
21 goes into 6 0 times with a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Include the next digit (7) from the dividend after 6, then repeat: 67 / 21

Advancing to step 2:
The number 21 fits into 67 3 times, leaving a remainder of 4.
Put 3 as the next digit of the answer. 
Result so far: 3.0
If we take 63 away from 67, we end up with 4.
Append the next digit (3) from the dividend to 4 and continue with: 43 / 21

Moving on to step 3:
21 goes into 43 2 times with a remainder of 1.
The number 2 becomes the next digit in our result. 
Result so far: 32.0
Deduct 42 from 43 and we're left with 1.
Fetch the next digit (3) from the dividend, attach it to 1 and continue: 13 / 21

Moving on to step 4:
The number 21 fits into 13 0 times, leaving a remainder of 13.
The number 0 becomes the next digit in our result. 
Result so far: 320.0
If we subtract 0 from 13, we get 13.
Include the next digit (9) from the dividend after 13, then repeat: 139 / 21

On to step 5:
When dividing 139 by 21, we get 6 with a remainder of 13.
Write down 6 as next digit of the result. 
Result so far: 3206.0
Subtracting 126 from 139 leaves us with 13.
Append the next digit (1) from the dividend to 13 and continue with: 131 / 21

Step 6:
The number 21 fits into 131 6 times, leaving a remainder of 5.
Put 6 as the next digit of the answer. 
Result so far: 32066.0
Subtract 126 from 131 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Moving on to step 7:
If we divide 50 by 21, we get 2 and a remainder of 8.
The next digit of our result is 2. 
Result so far: 32066.2
The remainder is 8 after subtracting 42 from 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

On to step 8:
If we divide 80 by 21, we get 3 and a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 32066.23
Subtract 63 from 80 to get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Step 9:
If we divide 170 by 21, we get 8 and a remainder of 2.
The number 8 becomes the next digit in our result. 
Result so far: 32066.238
The remainder is 2 after subtracting 168 from 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Advancing to step 10:
20 divided by 21 is 0 with a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 32066.238
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 11:
200 divided by 21 is 9 with a remainder of 11.
The next digit of our result is 9. 
Result so far: 32066.23809
If we take 189 away from 200, we end up with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

On to step 12:
21 goes into 110 5 times with a remainder of 5.
Write down 5 as next digit of the result. 
Result so far: 32066.238095
Deduct 105 from 110 and we're left with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Let's proceed to step 13:
21 can be fit into 50 2 times, resulting in a remainder of 8.
The next digit of our result is 2. 
Result so far: 32066.2380952
Subtracting 42 from 50 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Let's proceed to step 14:
21 can be fit into 80 3 times, resulting in a remainder of 17.
Record the quotient 3 as the next digit in the result. 
Result so far: 32066.23809523
The remainder is 17 after subtracting 63 from 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

The final result is 32066.23809523 with a remainder of 1.7e-08.