We look at the division of 591449 by 91 
The aim is to understand the frequency of 91 in 591449.

Going ahead to step 1:
If we divide 5 by 91, we get 0 and a remainder of 5.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 5 and we're left with 5.
Fetch the next digit (9) from the dividend, attach it to 5 and continue: 59 / 91

Advancing to step 2:
If we divide 59 by 91, we get 0 and a remainder of 59.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 59 and we're left with 59.
Append the next digit (1) from the dividend to 59 and continue with: 591 / 91

Going ahead to step 3:
When dividing 591 by 91, we get 6 with a remainder of 45.
Write down 6 as next digit of the result. 
Result so far: 6.0
The remainder is 45 after subtracting 546 from 591.
Include the next digit (4) from the dividend after 45, then repeat: 454 / 91

On to step 4:
91 can be fit into 454 4 times, resulting in a remainder of 90.
The number 4 becomes the next digit in our result. 
Result so far: 64.0
If we take 364 away from 454, we end up with 90.
Bring next digit (4) of the dividend behind the 90 and repeat the process: 904 / 91

On to step 5:
91 can be fit into 904 9 times, resulting in a remainder of 85.
Write down 9 as next digit of the result. 
Result so far: 649.0
Deduct 819 from 904 and we're left with 85.
Include the next digit (9) from the dividend after 85, then repeat: 859 / 91

Let's proceed to step 6:
91 can be fit into 859 9 times, resulting in a remainder of 40.
The next digit of our result is 9. 
Result so far: 6499.0
Subtract 819 from 859 to get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Step 7:
400 divided by 91 is 4 with a remainder of 36.
Use 4 as the next digit of our solution. 
Result so far: 6499.4
Subtract 364 from 400 to get 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Step 8:
When dividing 360 by 91, we get 3 with a remainder of 87.
Record the quotient 3 as the next digit in the result. 
Result so far: 6499.43
Subtracting 273 from 360 leaves us with 87.
Since there are no more digits in the dividend, we add a zero to the remainder making it 870, and continue the process.

Step 9:
91 goes into 870 9 times with a remainder of 51.
Write down 9 as next digit of the result. 
Result so far: 6499.439
Subtracting 819 from 870 leaves us with 51.
Since there are no more digits in the dividend, we add a zero to the remainder making it 510, and continue the process.

Step 10:
91 can be fit into 510 5 times, resulting in a remainder of 55.
The number 5 becomes the next digit in our result. 
Result so far: 6499.4395
Subtract 455 from 510 to get 55.
Since there are no more digits in the dividend, we add a zero to the remainder making it 550, and continue the process.

On to step 11:
If we divide 550 by 91, we get 6 and a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 6499.43956
Subtracting 546 from 550 leaves us 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.

On to step 12:
If we divide 40 by 91, we get 0 and a remainder of 40.
The number 0 becomes the next digit in our result. 
Result so far: 6499.43956
Deduct 0 from 40 and we're left with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Step 13:
91 goes into 400 4 times with a remainder of 36.
The number 4 becomes the next digit in our result. 
Result so far: 6499.4395604
Deduct 364 from 400 and we're left with 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Advancing to step 14:
360 divided by 91 is 3 with a remainder of 87.
The next digit of our result is 3. 
Result so far: 6499.43956043
If we subtract 273 from 360, we get 87.
Since there are no more digits in the dividend, we add a zero to the remainder making it 870, and continue the process.

After the division, we end up with 6499.43956043 and a remainder of 8.7e-08.