349707 ÷ 21 
The aim is to understand the frequency of 21 in 349707.

Let's proceed to step 1:
3 divided by 21 is 0 with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Include the next digit (4) from the dividend after 3, then repeat: 34 / 21

Going ahead to step 2:
When dividing 34 by 21, we get 1 with a remainder of 13.
Put 1 as the next digit of the answer. 
Result so far: 1.0
If we subtract 21 from 34, we get 13.
Append the next digit (9) from the dividend to 13 and continue with: 139 / 21

Let's proceed to step 3:
If we divide 139 by 21, we get 6 and a remainder of 13.
Record the quotient 6 as the next digit in the result. 
Result so far: 16.0
If we subtract 126 from 139, we get 13.
Include the next digit (7) from the dividend after 13, then repeat: 137 / 21

Going ahead to step 4:
21 can be fit into 137 6 times, resulting in a remainder of 11.
Use 6 as the next digit of our solution. 
Result so far: 166.0
If we subtract 126 from 137, we get 11.
Include the next digit (0) from the dividend after 11, then repeat: 110 / 21

Let's proceed to step 5:
The number 21 fits into 110 5 times, leaving a remainder of 5.
Write down 5 as next digit of the result. 
Result so far: 1665.0
If we subtract 105 from 110, we get 5.
Bring next digit (7) of the dividend behind the 5 and repeat the process: 57 / 21

On to step 6:
When dividing 57 by 21, we get 2 with a remainder of 15.
Record the quotient 2 as the next digit in the result. 
Result so far: 16652.0
Subtracting 42 from 57 leaves us 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.

Let's proceed to step 7:
When dividing 150 by 21, we get 7 with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 16652.7
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 8:
30 divided by 21 is 1 with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 16652.71
Deduct 21 from 30 and we're left 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.

Step 9:
The number 21 fits into 90 4 times, leaving a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 16652.714
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 10:
21 can be fit into 60 2 times, resulting in a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 16652.7142
If we take 42 away from 60, we end up 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.

Moving on to step 11:
180 divided by 21 is 8 with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 16652.71428
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.

Let's proceed to step 12:
The number 21 fits into 120 5 times, leaving a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 16652.714285
If we subtract 105 from 120, we get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Moving on to step 13:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Write down 7 as next digit of the result. 
Result so far: 16652.7142857
Subtract 147 from 150 to get 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 14:
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: 16652.71428571
Deduct 21 from 30 and we're left 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.

The final result is 16652.71428571 with a remainder of 9e-09.