We look at the division of 66659137 by 13 
The aim is to understand the frequency of 13 in 66659137.

Going ahead to step 1:
13 can be fit into 6 0 times, resulting in a remainder of 6.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 6 and we're left with 6.
Append the next digit (6) from the dividend to 6 and continue with: 66 / 13

Step 2:
13 can be fit into 66 5 times, resulting in a remainder of 1.
Use 5 as the next digit of our solution. 
Result so far: 5.0
Subtracting 65 from 66 leaves us with 1.
Bring next digit (6) of the dividend behind the 1 and repeat the process: 16 / 13

Going ahead to step 3:
If we divide 16 by 13, we get 1 and a remainder of 3.
Record the quotient 1 as the next digit in the result. 
Result so far: 51.0
The remainder is 3 after subtracting 13 from 16.
Grab the next digit (5) from the dividend, add it to 3, then carry on: 35 / 13

Step 4:
35 divided by 13 is 2 with a remainder of 9.
Put 2 as the next digit of the answer. 
Result so far: 512.0
The remainder is 9 after subtracting 26 from 35.
Append the next digit (9) from the dividend to 9 and continue with: 99 / 13

Advancing to step 5:
13 can be fit into 99 7 times, resulting in a remainder of 8.
Put 7 as the next digit of the answer. 
Result so far: 5127.0
If we subtract 91 from 99, we get 8.
Append the next digit (1) from the dividend to 8 and continue with: 81 / 13

On to step 6:
If we divide 81 by 13, we get 6 and a remainder of 3.
The number 6 becomes the next digit in our result. 
Result so far: 51276.0
Subtracting 78 from 81 leaves us with 3.
Take the next digit (3) from the dividend and append it to 3, then repeat: 33 / 13

Step 7:
The number 13 fits into 33 2 times, leaving a remainder of 7.
Put 2 as the next digit of the answer. 
Result so far: 512762.0
Subtracting 26 from 33 leaves us with 7.
Take the next digit (7) from the dividend and append it to 7, then repeat: 77 / 13

Moving on to step 8:
13 goes into 77 5 times with a remainder of 12.
Write down 5 as next digit of the result. 
Result so far: 5127625.0
Subtract 65 from 77 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Step 9:
13 can be fit into 120 9 times, resulting in a remainder of 3.
Record the quotient 9 as the next digit in the result. 
Result so far: 5127625.9
Subtracting 117 from 120 leaves us with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

On to step 10:
When dividing 30 by 13, we get 2 with a remainder of 4.
Use 2 as the next digit of our solution. 
Result so far: 5127625.92
The remainder is 4 after subtracting 26 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Let's proceed to step 11:
40 divided by 13 is 3 with a remainder of 1.
The next digit of our result is 3. 
Result so far: 5127625.923
If we subtract 39 from 40, we get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Let's proceed to step 12:
13 goes into 10 0 times with a remainder of 10.
Write down 0 as next digit of the result. 
Result so far: 5127625.923
The remainder is 10 after subtracting 0 from 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Step 13:
When dividing 100 by 13, we get 7 with a remainder of 9.
Put 7 as the next digit of the answer. 
Result so far: 5127625.92307
The remainder is 9 after subtracting 91 from 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Going ahead to step 14:
The number 13 fits into 90 6 times, leaving a remainder of 12.
Use 6 as the next digit of our solution. 
Result so far: 5127625.923076
If we take 78 away from 90, we end up with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Advancing to step 15:
The number 13 fits into 120 9 times, leaving a remainder of 3.
The next digit of our result is 9. 
Result so far: 5127625.9230769
The remainder is 3 after subtracting 117 from 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

On to step 16:
13 goes into 30 2 times with a remainder of 4.
Use 2 as the next digit of our solution. 
Result so far: 5127625.92307692
Subtract 26 from 30 to get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

The final outcome is 5127625.92307692, with a leftover of 4e-09.