Question 519324
If you multiply all the prime numbers less than 100,000 what is the units' digit of the product?
<pre>
<font color = "red">2</font>×3×<font color = "red">5</font>×7×11×13×17×19×···×99923×99929×99961×99971×99989×99991

Since 2 and 5 are factors of that huge number, so is 10, and every
integer of which 10 is a factor ends in 0.  And the units digit of
any integer is the digit it ends in.  Answer: 0

Edwin</pre>