Let's divide 668921 by 21
We want to figure out the number of times 668921 can be divided by 21.

Advancing to step 1:
21 goes into 6 0 times with a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 6 to get 6.
Bring next digit (6) of the dividend behind the 6 and repeat the process: 66 / 21

On to step 2:
21 goes into 66 3 times with a remainder of 3.
Write down 3 as next digit of the result. 
Result so far: 3.0
Deduct 63 from 66 and we're left with 3.
Bring next digit (8) of the dividend behind the 3 and repeat the process: 38 / 21

Step 3:
21 can be fit into 38 1 times, resulting in a remainder of 17.
The number 1 becomes the next digit in our result. 
Result so far: 31.0
Deduct 21 from 38 and we're left with 17.
Grab the next digit (9) from the dividend, add it to 17, then carry on: 179 / 21

Let's proceed to step 4:
179 divided by 21 is 8 with a remainder of 11.
The next digit of our result is 8. 
Result so far: 318.0
The remainder is 11 after subtracting 168 from 179.
Fetch the next digit (2) from the dividend, attach it to 11 and continue: 112 / 21

Going ahead to step 5:
The number 21 fits into 112 5 times, leaving a remainder of 7.
The number 5 becomes the next digit in our result. 
Result so far: 3185.0
If we subtract 105 from 112, we get 7.
Grab the next digit (1) from the dividend, add it to 7, then carry on: 71 / 21

Moving on to step 6:
71 divided by 21 is 3 with a remainder of 8.
Use 3 as the next digit of our solution. 
Result so far: 31853.0
The remainder is 8 after subtracting 63 from 71.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 7:
21 can be fit into 80 3 times, resulting in a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 31853.3
Deduct 63 from 80 and we're left with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Advancing to step 8:
21 can be fit into 170 8 times, resulting in a remainder of 2.
Write down 8 as next digit of the result. 
Result so far: 31853.38
If we subtract 168 from 170, we get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 9:
21 can be fit into 20 0 times, resulting in a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 31853.38
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.

On to step 10:
21 can be fit into 200 9 times, resulting in a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 31853.3809
Subtracting 189 from 200 leaves us 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.

Let's proceed to step 11:
If we divide 110 by 21, we get 5 and a remainder of 5.
Use 5 as the next digit of our solution. 
Result so far: 31853.38095
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.

Moving on to step 12:
If we divide 50 by 21, we get 2 and a remainder of 8.
Use 2 as the next digit of our solution. 
Result so far: 31853.380952
Subtract 42 from 50 to get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Advancing to step 13:
If we divide 80 by 21, we get 3 and a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 31853.3809523
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.

Let's proceed to step 14:
21 goes into 170 8 times with a remainder of 2.
Use 8 as the next digit of our solution. 
Result so far: 31853.38095238
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.

In conclusion, the division gives 31853.38095238 with a balance of 2e-09.