We're dividing 535733 by 21 
The aim is to understand the frequency of 21 in 535733.

Going ahead to step 1:
5 divided by 21 is 0 with a remainder of 5.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 5 after subtracting 0 from 5.
Grab the next digit (3) from the dividend, add it to 5, then carry on: 53 / 21

Going ahead to step 2:
If we divide 53 by 21, we get 2 and a remainder of 11.
Put 2 as the next digit of the answer. 
Result so far: 2.0
Deduct 42 from 53 and we're left with 11.
Bring next digit (5) of the dividend behind the 11 and repeat the process: 115 / 21

On to step 3:
When dividing 115 by 21, we get 5 with a remainder of 10.
Put 5 as the next digit of the answer. 
Result so far: 25.0
Deduct 105 from 115 and we're left with 10.
Bring next digit (7) of the dividend behind the 10 and repeat the process: 107 / 21

Moving on to step 4:
21 can be fit into 107 5 times, resulting in a remainder of 2.
Write down 5 as next digit of the result. 
Result so far: 255.0
Subtracting 105 from 107 leaves us with 2.
Append the next digit (3) from the dividend to 2 and continue with: 23 / 21

Going ahead to step 5:
When dividing 23 by 21, we get 1 with a remainder of 2.
Put 1 as the next digit of the answer. 
Result so far: 2551.0
Subtract 21 from 23 to get 2.
Append the next digit (3) from the dividend to 2 and continue with: 23 / 21

Advancing to step 6:
If we divide 23 by 21, we get 1 and a remainder of 2.
Use 1 as the next digit of our solution. 
Result so far: 25511.0
The remainder is 2 after subtracting 21 from 23.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

On to step 7:
20 divided by 21 is 0 with a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 25511.0
If we subtract 0 from 20, we 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 8:
21 can be fit into 200 9 times, resulting in a remainder of 11.
The next digit of our result is 9. 
Result so far: 25511.09
Subtracting 189 from 200 leaves us 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.

On to step 9:
21 goes into 110 5 times with a remainder of 5.
The next digit of our result is 5. 
Result so far: 25511.095
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.

Moving on to step 10:
21 goes into 50 2 times with a remainder of 8.
The next digit of our result is 2. 
Result so far: 25511.0952
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.

Advancing to step 11:
21 goes into 80 3 times with a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 25511.09523
Deduct 63 from 80 and we're left with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Step 12:
21 can be fit into 170 8 times, resulting in a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 25511.095238
The remainder is 2 after subtracting 168 from 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Advancing to step 13:
When dividing 20 by 21, we get 0 with a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 25511.095238
Subtracting 0 from 20 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 14:
21 goes into 200 9 times with a remainder of 11.
The next digit of our result is 9. 
Result so far: 25511.09523809
If we take 189 away from 200, we end up 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.

After the division, we end up with 25511.09523809 and a remainder of 1.1e-08.