wordpress URL end with a number

I am not sure if this is a known issue or suppose to be like this performance,

any wordpress website, if you put a number at the end of the URL, for example,

http://perishablepress.com/wordpress-multisite-mamp/
we put 1 or any numbers at the end

http://perishablepress.com/wordpress-multisite-mamp/123

We will not get the NOT FOUND page, we’ll still stay at the same page, which is

http://perishablepress.com/wordpress-multisite-mamp/

Is this an error or normal ? how do we redirect to NOT FOUND PAGE instead?