664191 ÷ 21 
We're looking to find how many times 21 goes into 664191.

Going ahead to step 1:
6 divided by 21 is 0 with a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Take the next digit (6) from the dividend and append it to 6, then repeat: 66 / 21

On to step 2:
66 divided by 21 is 3 with a remainder of 3.
Put 3 as the next digit of the answer. 
Result so far: 3.0
Subtracting 63 from 66 leaves us with 3.
Take the next digit (4) from the dividend and append it to 3, then repeat: 34 / 21

Moving on to step 3:
The number 21 fits into 34 1 times, leaving a remainder of 13.
Write down 1 as next digit of the result. 
Result so far: 31.0
Subtract 21 from 34 to get 13.
Append the next digit (1) from the dividend to 13 and continue with: 131 / 21

Advancing to step 4:
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: 316.0
The remainder is 5 after subtracting 126 from 131.
Bring next digit (9) of the dividend behind the 5 and repeat the process: 59 / 21

Let's proceed to step 5:
21 can be fit into 59 2 times, resulting in a remainder of 17.
The next digit of our result is 2. 
Result so far: 3162.0
The remainder is 17 after subtracting 42 from 59.
Take the next digit (1) from the dividend and append it to 17, then repeat: 171 / 21

On to step 6:
21 can be fit into 171 8 times, resulting in a remainder of 3.
Write down 8 as next digit of the result. 
Result so far: 31628.0
The remainder is 3 after subtracting 168 from 171.
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 7:
The number 21 fits into 30 1 times, leaving a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 31628.1
If we subtract 21 from 30, we get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Moving on to step 8:
90 divided by 21 is 4 with a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 31628.14
Subtract 84 from 90 to 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 9:
60 divided by 21 is 2 with a remainder of 18.
The number 2 becomes the next digit in our result. 
Result so far: 31628.142
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.

On to step 10:
180 divided by 21 is 8 with a remainder of 12.
The next digit of our result is 8. 
Result so far: 31628.1428
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.

Going ahead to step 11:
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: 31628.14285
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.

Going ahead to step 12:
150 divided by 21 is 7 with a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 31628.142857
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.

Going ahead to step 13:
The number 21 fits into 30 1 times, leaving a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 31628.1428571
Subtracting 21 from 30 leaves us 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.

Going ahead to step 14:
21 can be fit into 90 4 times, resulting in a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 31628.14285714
Subtract 84 from 90 to 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.

In conclusion, the division gives 31628.14285714 with a balance of 6e-09.