631758 ÷ 21 
The aim is to understand the frequency of 21 in 631758.

On to step 1:
If we divide 6 by 21, we get 0 and a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Bring next digit (3) of the dividend behind the 6 and repeat the process: 63 / 21

On to step 2:
21 goes into 63 3 times with a remainder of 0.
The next digit of our result is 3. 
Result so far: 3.0
Subtract 63 from 63 to get 0.
Grab the next digit (1) from the dividend, add it to 0, then carry on: 1 / 21

Going ahead to step 3:
21 goes into 1 0 times with a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 30.0
If we take 0 away from 1, we end up with 1.
Take the next digit (7) from the dividend and append it to 1, then repeat: 17 / 21

Moving on to step 4:
21 goes into 17 0 times with a remainder of 17.
Write down 0 as next digit of the result. 
Result so far: 300.0
Deduct 0 from 17 and we're left with 17.
Bring next digit (5) of the dividend behind the 17 and repeat the process: 175 / 21

Moving on to step 5:
21 can be fit into 175 8 times, resulting in a remainder of 7.
Record the quotient 8 as the next digit in the result. 
Result so far: 3008.0
The remainder is 7 after subtracting 168 from 175.
Include the next digit (8) from the dividend after 7, then repeat: 78 / 21

Going ahead to step 6:
If we divide 78 by 21, we get 3 and a remainder of 15.
Use 3 as the next digit of our solution. 
Result so far: 30083.0
Subtracting 63 from 78 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:
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: 30083.7
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.

Advancing to step 8:
21 goes into 30 1 times with a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 30083.71
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 9:
90 divided by 21 is 4 with a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 30083.714
Deduct 84 from 90 and we're left 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.

Going ahead to step 10:
60 divided by 21 is 2 with a remainder of 18.
The next digit of our result is 2. 
Result so far: 30083.7142
If we subtract 42 from 60, we get 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 11:
If we divide 180 by 21, we get 8 and a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 30083.71428
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.

Step 12:
The number 21 fits into 120 5 times, leaving a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 30083.714285
Subtracting 105 from 120 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.

Moving on to step 13:
21 goes into 150 7 times with a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 30083.7142857
If we subtract 147 from 150, we 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.

On to step 14:
The number 21 fits into 30 1 times, leaving a remainder of 9.
The number 1 becomes the next digit in our result. 
Result so far: 30083.71428571
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.

After the division, we end up with 30083.71428571 and a remainder of 9e-09.