91809891 ÷ 521 
Let's see how many times 521 fits into 91809891.

Going ahead to step 1:
The number 521 fits into 9 0 times, leaving a remainder of 9.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtract 0 from 9 to get 9.
Take the next digit (1) from the dividend and append it to 9, then repeat: 91 / 521

On to step 2:
If we divide 91 by 521, we get 0 and a remainder of 91.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 91 to get 91.
Append the next digit (8) from the dividend to 91 and continue with: 918 / 521

Advancing to step 3:
521 can be fit into 918 1 times, resulting in a remainder of 397.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
Subtracting 521 from 918 leaves us with 397.
Bring next digit (0) of the dividend behind the 397 and repeat the process: 3970 / 521

On to step 4:
If we divide 3970 by 521, we get 7 and a remainder of 323.
The number 7 becomes the next digit in our result. 
Result so far: 17.0
The remainder is 323 after subtracting 3647 from 3970.
Grab the next digit (9) from the dividend, add it to 323, then carry on: 3239 / 521

Advancing to step 5:
The number 521 fits into 3239 6 times, leaving a remainder of 113.
Use 6 as the next digit of our solution. 
Result so far: 176.0
If we take 3126 away from 3239, we end up with 113.
Bring next digit (8) of the dividend behind the 113 and repeat the process: 1138 / 521

Advancing to step 6:
1138 divided by 521 is 2 with a remainder of 96.
The next digit of our result is 2. 
Result so far: 1762.0
The remainder is 96 after subtracting 1042 from 1138.
Fetch the next digit (9) from the dividend, attach it to 96 and continue: 969 / 521

Advancing to step 7:
If we divide 969 by 521, we get 1 and a remainder of 448.
Use 1 as the next digit of our solution. 
Result so far: 17621.0
If we subtract 521 from 969, we get 448.
Grab the next digit (1) from the dividend, add it to 448, then carry on: 4481 / 521

Advancing to step 8:
521 can be fit into 4481 8 times, resulting in a remainder of 313.
The number 8 becomes the next digit in our result. 
Result so far: 176218.0
The remainder is 313 after subtracting 4168 from 4481.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3130, and continue the process.

Going ahead to step 9:
If we divide 3130 by 521, we get 6 and a remainder of 4.
Use 6 as the next digit of our solution. 
Result so far: 176218.6
Subtracting 3126 from 3130 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.

Step 10:
521 can be fit into 40 0 times, resulting in a remainder of 40.
The next digit of our result is 0. 
Result so far: 176218.6
Subtracting 0 from 40 leaves us 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 11:
If we divide 400 by 521, we get 0 and a remainder of 400.
The number 0 becomes the next digit in our result. 
Result so far: 176218.6
Deduct 0 from 400 and we're left with 400.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4000, and continue the process.

The final result is 176218.6 with a remainder of 0.04.