The product is 203770230 or 203,770,230. To do this by long multiplication, set out the numbers:
100330
2031 X
Take the last digit of 2031 and multiply the big number by it. Easy, because it's the big number again:
100330
Now take 3 next to the 1 and multiply by that, but leave a gap on the right underneath the 0:
100330
300990
The next digit in 2031 is 0, so we bypass that but leave an extra gap under 300990 before we multiply by 2:
100330
300990.
200660...
Now add up the aligned columns:
203770230