665389 ÷ 21 
Our goal is to divide 665389 by 21.

Going ahead to step 1:
6 divided by 21 is 0 with a remainder of 6.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 6 and we're left with 6.
Bring next digit (6) of the dividend behind the 6 and repeat the process: 66 / 21

Moving on to step 2:
If we divide 66 by 21, we get 3 and a remainder of 3.
The next digit of our result is 3. 
Result so far: 3.0
Subtracting 63 from 66 leaves us with 3.
Include the next digit (5) from the dividend after 3, then repeat: 35 / 21

Advancing to step 3:
When dividing 35 by 21, we get 1 with a remainder of 14.
Put 1 as the next digit of the answer. 
Result so far: 31.0
If we subtract 21 from 35, we get 14.
Include the next digit (3) from the dividend after 14, then repeat: 143 / 21

Moving on to step 4:
The number 21 fits into 143 6 times, leaving a remainder of 17.
Record the quotient 6 as the next digit in the result. 
Result so far: 316.0
Subtract 126 from 143 to get 17.
Take the next digit (8) from the dividend and append it to 17, then repeat: 178 / 21

Moving on to step 5:
When dividing 178 by 21, we get 8 with a remainder of 10.
The next digit of our result is 8. 
Result so far: 3168.0
Deduct 168 from 178 and we're left with 10.
Grab the next digit (9) from the dividend, add it to 10, then carry on: 109 / 21

Going ahead to step 6:
When dividing 109 by 21, we get 5 with a remainder of 4.
Write down 5 as next digit of the result. 
Result so far: 31685.0
If we take 105 away from 109, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Moving on to step 7:
21 can be fit into 40 1 times, resulting in a remainder of 19.
The next digit of our result is 1. 
Result so far: 31685.1
If we take 21 away from 40, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 8:
190 divided by 21 is 9 with a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 31685.19
If we subtract 189 from 190, we get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Advancing to step 9:
21 can be fit into 10 0 times, resulting in a remainder of 10.
Use 0 as the next digit of our solution. 
Result so far: 31685.19
Subtract 0 from 10 to get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Let's proceed to step 10:
21 goes into 100 4 times with a remainder of 16.
Record the quotient 4 as the next digit in the result. 
Result so far: 31685.1904
Subtracting 84 from 100 leaves us with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Let's proceed to step 11:
21 goes into 160 7 times with a remainder of 13.
The next digit of our result is 7. 
Result so far: 31685.19047
Subtracting 147 from 160 leaves us with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

On to step 12:
21 goes into 130 6 times with a remainder of 4.
Write down 6 as next digit of the result. 
Result so far: 31685.190476
If we take 126 away from 130, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Let's proceed to step 13:
21 can be fit into 40 1 times, resulting in a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 31685.1904761
Deduct 21 from 40 and we're left with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 14:
21 goes into 190 9 times with a remainder of 1.
Record the quotient 9 as the next digit in the result. 
Result so far: 31685.19047619
If we subtract 189 from 190, we get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Our division results in 31685.19047619 with a remaining 1e-09.