We look at the division of 487076 by 21 
The aim is to understand the frequency of 21 in 487076.

Advancing to step 1:
4 divided by 21 is 0 with a remainder of 4.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 4 to get 4.
Grab the next digit (8) from the dividend, add it to 4, then carry on: 48 / 21

Step 2:
If we divide 48 by 21, we get 2 and a remainder of 6.
The number 2 becomes the next digit in our result. 
Result so far: 2.0
Deduct 42 from 48 and we're left with 6.
Append the next digit (7) from the dividend to 6 and continue with: 67 / 21

On to step 3:
67 divided by 21 is 3 with a remainder of 4.
The number 3 becomes the next digit in our result. 
Result so far: 23.0
Subtracting 63 from 67 leaves us with 4.
Bring next digit (0) of the dividend behind the 4 and repeat the process: 40 / 21

Let's proceed to step 4:
If we divide 40 by 21, we get 1 and a remainder of 19.
Use 1 as the next digit of our solution. 
Result so far: 231.0
Deduct 21 from 40 and we're left with 19.
Fetch the next digit (7) from the dividend, attach it to 19 and continue: 197 / 21

Moving on to step 5:
The number 21 fits into 197 9 times, leaving a remainder of 8.
Record the quotient 9 as the next digit in the result. 
Result so far: 2319.0
Deduct 189 from 197 and we're left with 8.
Take the next digit (6) from the dividend and append it to 8, then repeat: 86 / 21

Step 6:
21 goes into 86 4 times with a remainder of 2.
Put 4 as the next digit of the answer. 
Result so far: 23194.0
If we take 84 away from 86, we end up with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Step 7:
If we divide 20 by 21, we get 0 and a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 23194.0
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:
200 divided by 21 is 9 with a remainder of 11.
The number 9 becomes the next digit in our result. 
Result so far: 23194.09
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.

Moving on to step 9:
21 can be fit into 110 5 times, resulting in a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 23194.095
The remainder is 5 after subtracting 105 from 110.
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 10:
When dividing 50 by 21, we get 2 with a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 23194.0952
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.

Advancing to step 11:
21 can be fit into 80 3 times, resulting in a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 23194.09523
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.

Let's proceed to step 12:
When dividing 170 by 21, we get 8 with a remainder of 2.
The next digit of our result is 8. 
Result so far: 23194.095238
Deduct 168 from 170 and we're left with 2.
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:
21 can be fit into 20 0 times, resulting in a remainder of 20.
The next digit of our result is 0. 
Result so far: 23194.095238
The remainder is 20 after subtracting 0 from 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:
If we divide 200 by 21, we get 9 and a remainder of 11.
The next digit of our result is 9. 
Result so far: 23194.09523809
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.

The final outcome is 23194.09523809, with a leftover of 1.1e-08.