640639 ÷ 13 
The aim is to understand the frequency of 13 in 640639.

On to step 1:
13 goes into 6 0 times with a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Bring next digit (4) of the dividend behind the 6 and repeat the process: 64 / 13

Moving on to step 2:
The number 13 fits into 64 4 times, leaving a remainder of 12.
The number 4 becomes the next digit in our result. 
Result so far: 4.0
The remainder is 12 after subtracting 52 from 64.
Include the next digit (0) from the dividend after 12, then repeat: 120 / 13

Let's proceed to step 3:
If we divide 120 by 13, we get 9 and a remainder of 3.
The number 9 becomes the next digit in our result. 
Result so far: 49.0
Subtracting 117 from 120 leaves us with 3.
Append the next digit (6) from the dividend to 3 and continue with: 36 / 13

Step 4:
The number 13 fits into 36 2 times, leaving a remainder of 10.
Put 2 as the next digit of the answer. 
Result so far: 492.0
If we subtract 26 from 36, we get 10.
Grab the next digit (3) from the dividend, add it to 10, then carry on: 103 / 13

Let's proceed to step 5:
If we divide 103 by 13, we get 7 and a remainder of 12.
Use 7 as the next digit of our solution. 
Result so far: 4927.0
Deduct 91 from 103 and we're left with 12.
Bring next digit (9) of the dividend behind the 12 and repeat the process: 129 / 13

Moving on to step 6:
If we divide 129 by 13, we get 9 and a remainder of 12.
The number 9 becomes the next digit in our result. 
Result so far: 49279.0
If we subtract 117 from 129, we 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.

On to step 7:
120 divided by 13 is 9 with a remainder of 3.
The next digit of our result is 9. 
Result so far: 49279.9
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 8:
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: 49279.92
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.

On to step 9:
The number 13 fits into 40 3 times, leaving a remainder of 1.
The number 3 becomes the next digit in our result. 
Result so far: 49279.923
The remainder is 1 after subtracting 39 from 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Going ahead to step 10:
13 goes into 10 0 times with a remainder of 10.
The next digit of our result is 0. 
Result so far: 49279.923
Deduct 0 from 10 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Going ahead to step 11:
If we divide 100 by 13, we get 7 and a remainder of 9.
Record the quotient 7 as the next digit in the result. 
Result so far: 49279.92307
Subtract 91 from 100 to get 9.
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 12:
13 can be fit into 90 6 times, resulting in a remainder of 12.
Record the quotient 6 as the next digit in the result. 
Result so far: 49279.923076
Subtracting 78 from 90 leaves us 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.

Let's proceed to step 13:
The number 13 fits into 120 9 times, leaving a remainder of 3.
Record the quotient 9 as the next digit in the result. 
Result so far: 49279.9230769
Subtract 117 from 120 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Let's proceed to step 14:
13 goes into 30 2 times with a remainder of 4.
The next digit of our result is 2. 
Result so far: 49279.92307692
If we take 26 away from 30, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

In conclusion, the division gives 49279.92307692 with a balance of 4e-09.