663991 divided by 42 
We want to divide 663991 by 42.

On to step 1:
42 goes into 6 0 times with a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 6 and we're left with 6.
Fetch the next digit (6) from the dividend, attach it to 6 and continue: 66 / 42

Going ahead to step 2:
42 goes into 66 1 times with a remainder of 24.
The next digit of our result is 1. 
Result so far: 1.0
The remainder is 24 after subtracting 42 from 66.
Bring next digit (3) of the dividend behind the 24 and repeat the process: 243 / 42

Going ahead to step 3:
243 divided by 42 is 5 with a remainder of 33.
The next digit of our result is 5. 
Result so far: 15.0
Subtract 210 from 243 to get 33.
Append the next digit (9) from the dividend to 33 and continue with: 339 / 42

Let's proceed to step 4:
The number 42 fits into 339 8 times, leaving a remainder of 3.
Record the quotient 8 as the next digit in the result. 
Result so far: 158.0
The remainder is 3 after subtracting 336 from 339.
Bring next digit (9) of the dividend behind the 3 and repeat the process: 39 / 42

Going ahead to step 5:
42 can be fit into 39 0 times, resulting in a remainder of 39.
Use 0 as the next digit of our solution. 
Result so far: 1580.0
Subtracting 0 from 39 leaves us with 39.
Fetch the next digit (1) from the dividend, attach it to 39 and continue: 391 / 42

Step 6:
When dividing 391 by 42, we get 9 with a remainder of 13.
Record the quotient 9 as the next digit in the result. 
Result so far: 15809.0
Subtract 378 from 391 to get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 7:
130 divided by 42 is 3 with a remainder of 4.
Put 3 as the next digit of the answer. 
Result so far: 15809.3
Subtract 126 from 130 to get 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 8:
42 can be fit into 40 0 times, resulting in a remainder of 40.
The next digit of our result is 0. 
Result so far: 15809.3
If we subtract 0 from 40, we 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.

Advancing to step 9:
42 goes into 400 9 times with a remainder of 22.
Put 9 as the next digit of the answer. 
Result so far: 15809.309
Deduct 378 from 400 and we're left with 22.
Since there are no more digits in the dividend, we add a zero to the remainder making it 220, and continue the process.

Moving on to step 10:
If we divide 220 by 42, we get 5 and a remainder of 10.
Record the quotient 5 as the next digit in the result. 
Result so far: 15809.3095
The remainder is 10 after subtracting 210 from 220.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Step 11:
The number 42 fits into 100 2 times, leaving a remainder of 16.
Use 2 as the next digit of our solution. 
Result so far: 15809.30952
If we subtract 84 from 100, 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.

Let's proceed to step 12:
When dividing 160 by 42, we get 3 with a remainder of 34.
Use 3 as the next digit of our solution. 
Result so far: 15809.309523
The remainder is 34 after subtracting 126 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 340, and continue the process.

Step 13:
42 goes into 340 8 times with a remainder of 4.
The next digit of our result is 8. 
Result so far: 15809.3095238
The remainder is 4 after subtracting 336 from 340.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Let's proceed to step 14:
The number 42 fits into 40 0 times, leaving a remainder of 40.
Use 0 as the next digit of our solution. 
Result so far: 15809.3095238
Subtract 0 from 40 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.

The final outcome is 15809.3095238, with a leftover of 4e-08.