We're dividing 687281 by 21 
The aim is to understand the frequency of 21 in 687281.

Going ahead to step 1:
When dividing 6 by 21, we get 0 with a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 6, we get 6.
Append the next digit (8) from the dividend to 6 and continue with: 68 / 21

Step 2:
21 can be fit into 68 3 times, resulting in a remainder of 5.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Deduct 63 from 68 and we're left with 5.
Include the next digit (7) from the dividend after 5, then repeat: 57 / 21

Going ahead to step 3:
The number 21 fits into 57 2 times, leaving a remainder of 15.
The number 2 becomes the next digit in our result. 
Result so far: 32.0
Deduct 42 from 57 and we're left with 15.
Bring next digit (2) of the dividend behind the 15 and repeat the process: 152 / 21

Moving on to step 4:
21 goes into 152 7 times with a remainder of 5.
Write down 7 as next digit of the result. 
Result so far: 327.0
Deduct 147 from 152 and we're left with 5.
Grab the next digit (8) from the dividend, add it to 5, then carry on: 58 / 21

Step 5:
The number 21 fits into 58 2 times, leaving a remainder of 16.
The number 2 becomes the next digit in our result. 
Result so far: 3272.0
Subtract 42 from 58 to get 16.
Append the next digit (1) from the dividend to 16 and continue with: 161 / 21

Advancing to step 6:
The number 21 fits into 161 7 times, leaving a remainder of 14.
The number 7 becomes the next digit in our result. 
Result so far: 32727.0
Subtract 147 from 161 to get 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Moving on to step 7:
When dividing 140 by 21, we get 6 with a remainder of 14.
The number 6 becomes the next digit in our result. 
Result so far: 32727.6
Subtracting 126 from 140 leaves us with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Let's proceed to step 8:
When dividing 140 by 21, we get 6 with a remainder of 14.
Put 6 as the next digit of the answer. 
Result so far: 32727.66
The remainder is 14 after subtracting 126 from 140.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

The final outcome is 32727.66, with a leftover of 0.014.