406689 ÷ 21 
We're looking to find how many times 21 goes into 406689.

On to step 1:
4 divided by 21 is 0 with a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtracting 0 from 4 leaves us with 4.
Include the next digit (0) from the dividend after 4, then repeat: 40 / 21

On to step 2:
21 can be fit into 40 1 times, resulting in a remainder of 19.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
If we take 21 away from 40, we end up with 19.
Bring next digit (6) of the dividend behind the 19 and repeat the process: 196 / 21

Moving on to step 3:
196 divided by 21 is 9 with a remainder of 7.
Write down 9 as next digit of the result. 
Result so far: 19.0
If we take 189 away from 196, we end up with 7.
Bring next digit (6) of the dividend behind the 7 and repeat the process: 76 / 21

Going ahead to step 4:
When dividing 76 by 21, we get 3 with a remainder of 13.
Put 3 as the next digit of the answer. 
Result so far: 193.0
If we take 63 away from 76, we end up with 13.
Include the next digit (8) from the dividend after 13, then repeat: 138 / 21

Going ahead to step 5:
The number 21 fits into 138 6 times, leaving a remainder of 12.
The next digit of our result is 6. 
Result so far: 1936.0
Subtract 126 from 138 to get 12.
Fetch the next digit (9) from the dividend, attach it to 12 and continue: 129 / 21

Let's proceed to step 6:
21 can be fit into 129 6 times, resulting in a remainder of 3.
Record the quotient 6 as the next digit in the result. 
Result so far: 19366.0
If we take 126 away from 129, 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.

On to step 7:
21 can be fit into 30 1 times, resulting in a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 19366.1
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.

On to step 8:
If we divide 90 by 21, we get 4 and a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 19366.14
Subtracting 84 from 90 leaves us 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.

Let's proceed to step 9:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 19366.142
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.

Let's proceed to step 10:
If we divide 180 by 21, we get 8 and a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 19366.1428
If we take 168 away from 180, we end up 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.

Step 11:
If we divide 120 by 21, we get 5 and a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 19366.14285
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.

On to step 12:
21 goes into 150 7 times with a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 19366.142857
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.

Step 13:
The number 21 fits into 30 1 times, leaving a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 19366.1428571
Subtract 21 from 30 to 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.

Step 14:
When dividing 90 by 21, we get 4 with a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 19366.14285714
Subtracting 84 from 90 leaves us 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.

The quotient of the division is 19366.14285714, and the remainder is 6e-09.