We look at the division of 15107151 by 81 
The aim is to understand the frequency of 81 in 15107151.

On to step 1:
The number 81 fits into 1 0 times, leaving a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Bring next digit (5) of the dividend behind the 1 and repeat the process: 15 / 81

Moving on to step 2:
81 goes into 15 0 times with a remainder of 15.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 15 leaves us with 15.
Grab the next digit (1) from the dividend, add it to 15, then carry on: 151 / 81

Advancing to step 3:
When dividing 151 by 81, we get 1 with a remainder of 70.
Put 1 as the next digit of the answer. 
Result so far: 1.0
The remainder is 70 after subtracting 81 from 151.
Include the next digit (0) from the dividend after 70, then repeat: 700 / 81

Let's proceed to step 4:
700 divided by 81 is 8 with a remainder of 52.
Put 8 as the next digit of the answer. 
Result so far: 18.0
Deduct 648 from 700 and we're left with 52.
Grab the next digit (7) from the dividend, add it to 52, then carry on: 527 / 81

Let's proceed to step 5:
If we divide 527 by 81, we get 6 and a remainder of 41.
Record the quotient 6 as the next digit in the result. 
Result so far: 186.0
If we take 486 away from 527, we end up with 41.
Bring next digit (1) of the dividend behind the 41 and repeat the process: 411 / 81

Going ahead to step 6:
81 goes into 411 5 times with a remainder of 6.
The number 5 becomes the next digit in our result. 
Result so far: 1865.0
Subtracting 405 from 411 leaves us with 6.
Bring next digit (5) of the dividend behind the 6 and repeat the process: 65 / 81

On to step 7:
81 goes into 65 0 times with a remainder of 65.
Use 0 as the next digit of our solution. 
Result so far: 18650.0
Subtract 0 from 65 to get 65.
Bring next digit (1) of the dividend behind the 65 and repeat the process: 651 / 81

Let's proceed to step 8:
When dividing 651 by 81, we get 8 with a remainder of 3.
Put 8 as the next digit of the answer. 
Result so far: 186508.0
If we subtract 648 from 651, we 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.

Step 9:
81 can be fit into 30 0 times, resulting in a remainder of 30.
Put 0 as the next digit of the answer. 
Result so far: 186508.0
Subtract 0 from 30 to get 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

On to step 10:
81 goes into 300 3 times with a remainder of 57.
Write down 3 as next digit of the result. 
Result so far: 186508.03
Subtracting 243 from 300 leaves us with 57.
Since there are no more digits in the dividend, we add a zero to the remainder making it 570, and continue the process.

Going ahead to step 11:
If we divide 570 by 81, we get 7 and a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 186508.037
The remainder is 3 after subtracting 567 from 570.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Advancing to step 12:
30 divided by 81 is 0 with a remainder of 30.
Use 0 as the next digit of our solution. 
Result so far: 186508.037
The remainder is 30 after subtracting 0 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Advancing to step 13:
If we divide 300 by 81, we get 3 and a remainder of 57.
Record the quotient 3 as the next digit in the result. 
Result so far: 186508.03703
Deduct 243 from 300 and we're left with 57.
Since there are no more digits in the dividend, we add a zero to the remainder making it 570, and continue the process.

Let's proceed to step 14:
When dividing 570 by 81, we get 7 with a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 186508.037037
If we subtract 567 from 570, we 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.

Advancing to step 15:
30 divided by 81 is 0 with a remainder of 30.
Put 0 as the next digit of the answer. 
Result so far: 186508.037037
Subtracting 0 from 30 leaves us with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Moving on to step 16:
81 goes into 300 3 times with a remainder of 57.
The number 3 becomes the next digit in our result. 
Result so far: 186508.03703703
If we subtract 243 from 300, we get 57.
Since there are no more digits in the dividend, we add a zero to the remainder making it 570, and continue the process.

In conclusion, the division gives 186508.03703703 with a balance of 5.7e-08.