We look at the division of 767748 by 21 
The aim is to understand the frequency of 21 in 767748.

Let's proceed to step 1:
The number 21 fits into 7 0 times, leaving a remainder of 7.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 7 to get 7.
Append the next digit (6) from the dividend to 7 and continue with: 76 / 21

Step 2:
76 divided by 21 is 3 with a remainder of 13.
The next digit of our result is 3. 
Result so far: 3.0
The remainder is 13 after subtracting 63 from 76.
Append the next digit (7) from the dividend to 13 and continue with: 137 / 21

Step 3:
21 can be fit into 137 6 times, resulting in a remainder of 11.
The next digit of our result is 6. 
Result so far: 36.0
The remainder is 11 after subtracting 126 from 137.
Grab the next digit (7) from the dividend, add it to 11, then carry on: 117 / 21

Advancing to step 4:
The number 21 fits into 117 5 times, leaving a remainder of 12.
The number 5 becomes the next digit in our result. 
Result so far: 365.0
Subtract 105 from 117 to get 12.
Grab the next digit (4) from the dividend, add it to 12, then carry on: 124 / 21

Step 5:
If we divide 124 by 21, we get 5 and a remainder of 19.
Record the quotient 5 as the next digit in the result. 
Result so far: 3655.0
The remainder is 19 after subtracting 105 from 124.
Take the next digit (8) from the dividend and append it to 19, then repeat: 198 / 21

On to step 6:
If we divide 198 by 21, we get 9 and a remainder of 9.
Put 9 as the next digit of the answer. 
Result so far: 36559.0
The remainder is 9 after subtracting 189 from 198.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 7:
When dividing 90 by 21, we get 4 with a remainder of 6.
The next digit of our result is 4. 
Result so far: 36559.4
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 8:
21 goes into 60 2 times with a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 36559.42
Deduct 42 from 60 and we're left 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.

Advancing to step 9:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 36559.428
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.

Advancing to step 10:
21 can be fit into 120 5 times, resulting in a remainder of 15.
The number 5 becomes the next digit in our result. 
Result so far: 36559.4285
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.

Step 11:
21 can be fit into 150 7 times, resulting in a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 36559.42857
If we take 147 away from 150, 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.

Let's proceed to step 12:
When dividing 30 by 21, we get 1 with a remainder of 9.
The number 1 becomes the next digit in our result. 
Result so far: 36559.428571
The remainder is 9 after subtracting 21 from 30.
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 13:
When dividing 90 by 21, we get 4 with a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 36559.4285714
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.

Moving on to step 14:
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: 36559.42857142
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.

After the division, we end up with 36559.42857142 and a remainder of 1.8e-08.