171990 divided by 4 
We want to divide 171990 by 4.

Going ahead to step 1:
4 can be fit into 1 0 times, resulting in a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Include the next digit (7) from the dividend after 1, then repeat: 17 / 4

On to step 2:
When dividing 17 by 4, we get 4 with a remainder of 1.
Record the quotient 4 as the next digit in the result. 
Result so far: 4.0
Deduct 16 from 17 and we're left with 1.
Take the next digit (1) from the dividend and append it to 1, then repeat: 11 / 4

Advancing to step 3:
If we divide 11 by 4, we get 2 and a remainder of 3.
Put 2 as the next digit of the answer. 
Result so far: 42.0
If we subtract 8 from 11, we get 3.
Fetch the next digit (9) from the dividend, attach it to 3 and continue: 39 / 4

Step 4:
If we divide 39 by 4, we get 9 and a remainder of 3.
Put 9 as the next digit of the answer. 
Result so far: 429.0
The remainder is 3 after subtracting 36 from 39.
Take the next digit (9) from the dividend and append it to 3, then repeat: 39 / 4

Advancing to step 5:
If we divide 39 by 4, we get 9 and a remainder of 3.
The number 9 becomes the next digit in our result. 
Result so far: 4299.0
Subtract 36 from 39 to get 3.
Bring next digit (0) of the dividend behind the 3 and repeat the process: 30 / 4

Let's proceed to step 6:
30 divided by 4 is 7 with a remainder of 2.
Write down 7 as next digit of the result. 
Result so far: 42997.0
Deduct 28 from 30 and we're left with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 7:
20 divided by 4 is 5 with a remainder of 0.
The number 5 becomes the next digit in our result. 
Result so far: 42997.5
The remainder is 0 after subtracting 20 from 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Advancing to step 8:
0 divided by 4 is 0 with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 42997.5
If we take 0 away from 0, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Moving on to step 9:
0 divided by 4 is 0 with a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 42997.5
Subtracting 0 from 0 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The final outcome is 42997.5, with a leftover of 0.0.