We look at the division of 873925 by 81 
The aim is to understand the frequency of 81 in 873925.

Going ahead to step 1:
8 divided by 81 is 0 with a remainder of 8.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 8, we get 8.
Append the next digit (7) from the dividend to 8 and continue with: 87 / 81

Step 2:
The number 81 fits into 87 1 times, leaving a remainder of 6.
Put 1 as the next digit of the answer. 
Result so far: 1.0
Subtract 81 from 87 to get 6.
Take the next digit (3) from the dividend and append it to 6, then repeat: 63 / 81

Step 3:
81 goes into 63 0 times with a remainder of 63.
Put 0 as the next digit of the answer. 
Result so far: 10.0
Subtracting 0 from 63 leaves us with 63.
Grab the next digit (9) from the dividend, add it to 63, then carry on: 639 / 81

Step 4:
If we divide 639 by 81, we get 7 and a remainder of 72.
The number 7 becomes the next digit in our result. 
Result so far: 107.0
If we subtract 567 from 639, we get 72.
Append the next digit (2) from the dividend to 72 and continue with: 722 / 81

Moving on to step 5:
When dividing 722 by 81, we get 8 with a remainder of 74.
Put 8 as the next digit of the answer. 
Result so far: 1078.0
Subtract 648 from 722 to get 74.
Include the next digit (5) from the dividend after 74, then repeat: 745 / 81

Advancing to step 6:
If we divide 745 by 81, we get 9 and a remainder of 16.
Put 9 as the next digit of the answer. 
Result so far: 10789.0
If we subtract 729 from 745, we get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Step 7:
81 goes into 160 1 times with a remainder of 79.
Write down 1 as next digit of the result. 
Result so far: 10789.1
Subtracting 81 from 160 leaves us with 79.
Since there are no more digits in the dividend, we add a zero to the remainder making it 790, and continue the process.

Going ahead to step 8:
81 can be fit into 790 9 times, resulting in a remainder of 61.
Use 9 as the next digit of our solution. 
Result so far: 10789.19
Subtract 729 from 790 to get 61.
Since there are no more digits in the dividend, we add a zero to the remainder making it 610, and continue the process.

Going ahead to step 9:
81 can be fit into 610 7 times, resulting in a remainder of 43.
The next digit of our result is 7. 
Result so far: 10789.197
If we take 567 away from 610, we end up with 43.
Since there are no more digits in the dividend, we add a zero to the remainder making it 430, and continue the process.

On to step 10:
If we divide 430 by 81, we get 5 and a remainder of 25.
Record the quotient 5 as the next digit in the result. 
Result so far: 10789.1975
Deduct 405 from 430 and we're left with 25.
Since there are no more digits in the dividend, we add a zero to the remainder making it 250, and continue the process.

Advancing to step 11:
250 divided by 81 is 3 with a remainder of 7.
Write down 3 as next digit of the result. 
Result so far: 10789.19753
The remainder is 7 after subtracting 243 from 250.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Advancing to step 12:
70 divided by 81 is 0 with a remainder of 70.
The next digit of our result is 0. 
Result so far: 10789.19753
Subtracting 0 from 70 leaves us with 70.
Since there are no more digits in the dividend, we add a zero to the remainder making it 700, and continue the process.

Moving on to step 13:
700 divided by 81 is 8 with a remainder of 52.
Put 8 as the next digit of the answer. 
Result so far: 10789.1975308
The remainder is 52 after subtracting 648 from 700.
Since there are no more digits in the dividend, we add a zero to the remainder making it 520, and continue the process.

Going ahead to step 14:
If we divide 520 by 81, we get 6 and a remainder of 34.
The number 6 becomes the next digit in our result. 
Result so far: 10789.19753086
Subtract 486 from 520 to get 34.
Since there are no more digits in the dividend, we add a zero to the remainder making it 340, and continue the process.

Our division results in 10789.19753086 with a remaining 3.4e-08.