We divide 644390 by 31
We're looking to find how many times 31 goes into 644390.

Going ahead to step 1:
If we divide 6 by 31, 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 subtract 0 from 6, we get 6.
Include the next digit (4) from the dividend after 6, then repeat: 64 / 31

Going ahead to step 2:
If we divide 64 by 31, we get 2 and a remainder of 2.
Record the quotient 2 as the next digit in the result. 
Result so far: 2.0
Subtracting 62 from 64 leaves us with 2.
Include the next digit (4) from the dividend after 2, then repeat: 24 / 31

Advancing to step 3:
31 goes into 24 0 times with a remainder of 24.
The next digit of our result is 0. 
Result so far: 20.0
Subtracting 0 from 24 leaves us with 24.
Append the next digit (3) from the dividend to 24 and continue with: 243 / 31

Step 4:
The number 31 fits into 243 7 times, leaving a remainder of 26.
Put 7 as the next digit of the answer. 
Result so far: 207.0
The remainder is 26 after subtracting 217 from 243.
Append the next digit (9) from the dividend to 26 and continue with: 269 / 31

Moving on to step 5:
When dividing 269 by 31, we get 8 with a remainder of 21.
Record the quotient 8 as the next digit in the result. 
Result so far: 2078.0
The remainder is 21 after subtracting 248 from 269.
Include the next digit (0) from the dividend after 21, then repeat: 210 / 31

On to step 6:
31 can be fit into 210 6 times, resulting in a remainder of 24.
Put 6 as the next digit of the answer. 
Result so far: 20786.0
If we subtract 186 from 210, we get 24.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

Let's proceed to step 7:
The number 31 fits into 240 7 times, leaving a remainder of 23.
Put 7 as the next digit of the answer. 
Result so far: 20786.7
If we take 217 away from 240, we end up with 23.
Since there are no more digits in the dividend, we add a zero to the remainder making it 230, and continue the process.

Step 8:
31 can be fit into 230 7 times, resulting in a remainder of 13.
The next digit of our result is 7. 
Result so far: 20786.77
If we subtract 217 from 230, we 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.

The final outcome is 20786.77, with a leftover of 0.013.