663591 ÷ 90 
We want to figure out the number of times 663591 can be divided by 90.

Moving on to step 1:
If we divide 6 by 90, we get 0 and a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Grab the next digit (6) from the dividend, add it to 6, then carry on: 66 / 90

Advancing to step 2:
The number 90 fits into 66 0 times, leaving a remainder of 66.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 66 and we're left with 66.
Include the next digit (3) from the dividend after 66, then repeat: 663 / 90

On to step 3:
The number 90 fits into 663 7 times, leaving a remainder of 33.
Put 7 as the next digit of the answer. 
Result so far: 7.0
Subtracting 630 from 663 leaves us with 33.
Append the next digit (5) from the dividend to 33 and continue with: 335 / 90

Let's proceed to step 4:
The number 90 fits into 335 3 times, leaving a remainder of 65.
Write down 3 as next digit of the result. 
Result so far: 73.0
Deduct 270 from 335 and we're left with 65.
Bring next digit (9) of the dividend behind the 65 and repeat the process: 659 / 90

Going ahead to step 5:
The number 90 fits into 659 7 times, leaving a remainder of 29.
Record the quotient 7 as the next digit in the result. 
Result so far: 737.0
Deduct 630 from 659 and we're left with 29.
Take the next digit (1) from the dividend and append it to 29, then repeat: 291 / 90

Advancing to step 6:
90 goes into 291 3 times with a remainder of 21.
Record the quotient 3 as the next digit in the result. 
Result so far: 7373.0
Subtract 270 from 291 to get 21.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Going ahead to step 7:
If we divide 210 by 90, we get 2 and a remainder of 30.
Put 2 as the next digit of the answer. 
Result so far: 7373.2
Subtracting 180 from 210 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.

On to step 8:
300 divided by 90 is 3 with a remainder of 30.
The next digit of our result is 3. 
Result so far: 7373.23
The remainder is 30 after subtracting 270 from 300.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Step 9:
90 goes into 300 3 times with a remainder of 30.
The next digit of our result is 3. 
Result so far: 7373.233
Subtract 270 from 300 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.

In conclusion, the division gives 7373.233 with a balance of 0.003.