Block one specific URL by htaccess

When someone requests:

https://www.mathelounge.de/40224/redaktionelle-frage-wann-antwort-wann-lediglich-kommentar

The %{REQUEST_URI} variable is:

/40224/redaktionelle-frage-wann-antwort-wann-lediglich-kommentar

And the regex ^40224\/$ will never match that. In fact, you don't even need a RewriteCond in this instance, just put the pattern in the rule:

RewriteRule ^40224/redaktionelle-frage-wann-antwort-wann-lediglich-kommentar$ - [F]

Note that the pattern in the rule itself doesn't lead with a /, it's because for the rule, it's stripped off, but for the %{REQUEST_URI} var, it's preserved.

this can also be used:

RewriteCond %{HTTP_REFERER} 40224/redaktionelle-frage-wann-antwort-wann-lediglich-kommentar [NC,OR]