We look at the division of 538367 by 21 
The aim is to understand the frequency of 21 in 538367.

Step 1:
21 can be fit into 5 0 times, resulting in a remainder of 5.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 5, we get 5.
Append the next digit (3) from the dividend to 5 and continue with: 53 / 21

Moving on to step 2:
The number 21 fits into 53 2 times, leaving a remainder of 11.
Put 2 as the next digit of the answer. 
Result so far: 2.0
If we subtract 42 from 53, we get 11.
Grab the next digit (8) from the dividend, add it to 11, then carry on: 118 / 21

Going ahead to step 3:
If we divide 118 by 21, we get 5 and a remainder of 13.
Write down 5 as next digit of the result. 
Result so far: 25.0
Subtracting 105 from 118 leaves us with 13.
Grab the next digit (3) from the dividend, add it to 13, then carry on: 133 / 21

Going ahead to step 4:
If we divide 133 by 21, we get 6 and a remainder of 7.
Record the quotient 6 as the next digit in the result. 
Result so far: 256.0
Subtract 126 from 133 to get 7.
Bring next digit (6) of the dividend behind the 7 and repeat the process: 76 / 21

Let's proceed to step 5:
76 divided by 21 is 3 with a remainder of 13.
The next digit of our result is 3. 
Result so far: 2563.0
If we take 63 away from 76, we end up with 13.
Include the next digit (7) from the dividend after 13, then repeat: 137 / 21

Step 6:
If we divide 137 by 21, we get 6 and a remainder of 11.
Use 6 as the next digit of our solution. 
Result so far: 25636.0
If we subtract 126 from 137, we get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Advancing to step 7:
110 divided by 21 is 5 with a remainder of 5.
Use 5 as the next digit of our solution. 
Result so far: 25636.5
If we subtract 105 from 110, we get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Going ahead to step 8:
If we divide 50 by 21, we get 2 and a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 25636.52
If we take 42 away from 50, we end up with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 9:
21 can be fit into 80 3 times, resulting in a remainder of 17.
The next digit of our result is 3. 
Result so far: 25636.523
If we subtract 63 from 80, we get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Moving on to step 10:
The number 21 fits into 170 8 times, leaving a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 25636.5238
If we subtract 168 from 170, we get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Going ahead to step 11:
When dividing 20 by 21, we get 0 with a remainder of 20.
Record the quotient 0 as the next digit in the result. 
Result so far: 25636.5238
Subtract 0 from 20 to get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 12:
200 divided by 21 is 9 with a remainder of 11.
The number 9 becomes the next digit in our result. 
Result so far: 25636.523809
Deduct 189 from 200 and we're left with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Step 13:
21 can be fit into 110 5 times, resulting in a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 25636.5238095
Subtract 105 from 110 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Going ahead to step 14:
50 divided by 21 is 2 with a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 25636.52380952
Subtracting 42 from 50 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

The quotient of the division is 25636.52380952, and the remainder is 8e-09.