Let's divide 647591 by 21
The aim is to understand the frequency of 21 in 647591.

Going ahead to step 1:
6 divided by 21 is 0 with a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Append the next digit (4) from the dividend to 6 and continue with: 64 / 21

Let's proceed to step 2:
21 goes into 64 3 times with a remainder of 1.
Write down 3 as next digit of the result. 
Result so far: 3.0
Subtract 63 from 64 to get 1.
Grab the next digit (7) from the dividend, add it to 1, then carry on: 17 / 21

Let's proceed to step 3:
When dividing 17 by 21, we get 0 with a remainder of 17.
The next digit of our result is 0. 
Result so far: 30.0
If we subtract 0 from 17, we get 17.
Take the next digit (5) from the dividend and append it to 17, then repeat: 175 / 21

Going ahead to step 4:
175 divided by 21 is 8 with a remainder of 7.
Write down 8 as next digit of the result. 
Result so far: 308.0
If we take 168 away from 175, we end up with 7.
Bring next digit (9) of the dividend behind the 7 and repeat the process: 79 / 21

On to step 5:
79 divided by 21 is 3 with a remainder of 16.
The next digit of our result is 3. 
Result so far: 3083.0
Subtracting 63 from 79 leaves us with 16.
Grab the next digit (1) from the dividend, add it to 16, then carry on: 161 / 21

Advancing to step 6:
21 can be fit into 161 7 times, resulting in a remainder of 14.
The next digit of our result is 7. 
Result so far: 30837.0
The remainder is 14 after subtracting 147 from 161.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Step 7:
If we divide 140 by 21, we get 6 and a remainder of 14.
The next digit of our result is 6. 
Result so far: 30837.6
Subtract 126 from 140 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 8:
140 divided by 21 is 6 with a remainder of 14.
Record the quotient 6 as the next digit in the result. 
Result so far: 30837.66
If we take 126 away from 140, we end up 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.

The final result is 30837.66 with a remainder of 0.014.