We look at the division of 864021 by 13 
The aim is to understand the frequency of 13 in 864021.

Going ahead to step 1:
If we divide 8 by 13, we get 0 and a remainder of 8.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 8 leaves us with 8.
Bring next digit (6) of the dividend behind the 8 and repeat the process: 86 / 13

Going ahead to step 2:
When dividing 86 by 13, we get 6 with a remainder of 8.
Record the quotient 6 as the next digit in the result. 
Result so far: 6.0
If we take 78 away from 86, we end up with 8.
Bring next digit (4) of the dividend behind the 8 and repeat the process: 84 / 13

On to step 3:
When dividing 84 by 13, we get 6 with a remainder of 6.
The number 6 becomes the next digit in our result. 
Result so far: 66.0
Subtracting 78 from 84 leaves us with 6.
Take the next digit (0) from the dividend and append it to 6, then repeat: 60 / 13

Advancing to step 4:
60 divided by 13 is 4 with a remainder of 8.
Write down 4 as next digit of the result. 
Result so far: 664.0
Subtract 52 from 60 to get 8.
Take the next digit (2) from the dividend and append it to 8, then repeat: 82 / 13

Step 5:
The number 13 fits into 82 6 times, leaving a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 6646.0
Deduct 78 from 82 and we're left with 4.
Append the next digit (1) from the dividend to 4 and continue with: 41 / 13

Let's proceed to step 6:
If we divide 41 by 13, we get 3 and a remainder of 2.
The next digit of our result is 3. 
Result so far: 66463.0
Deduct 39 from 41 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.

On to step 7:
13 goes into 20 1 times with a remainder of 7.
Write down 1 as next digit of the result. 
Result so far: 66463.1
Subtracting 13 from 20 leaves us with 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Step 8:
The number 13 fits into 70 5 times, leaving a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 66463.15
Deduct 65 from 70 and we're left with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

On to step 9:
50 divided by 13 is 3 with a remainder of 11.
The number 3 becomes the next digit in our result. 
Result so far: 66463.153
Subtract 39 from 50 to 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.

Going ahead to step 10:
13 goes into 110 8 times with a remainder of 6.
Use 8 as the next digit of our solution. 
Result so far: 66463.1538
The remainder is 6 after subtracting 104 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 11:
If we divide 60 by 13, we get 4 and a remainder of 8.
Use 4 as the next digit of our solution. 
Result so far: 66463.15384
Subtracting 52 from 60 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.

Moving on to step 12:
13 can be fit into 80 6 times, resulting in a remainder of 2.
Use 6 as the next digit of our solution. 
Result so far: 66463.153846
If we subtract 78 from 80, 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.

Let's proceed to step 13:
When dividing 20 by 13, we get 1 with a remainder of 7.
Record the quotient 1 as the next digit in the result. 
Result so far: 66463.1538461
If we subtract 13 from 20, we get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

On to step 14:
70 divided by 13 is 5 with a remainder of 5.
The number 5 becomes the next digit in our result. 
Result so far: 66463.15384615
Deduct 65 from 70 and we're left with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

In conclusion, the division gives 66463.15384615 with a balance of 5e-09.