Regex: only alphanumeric but not if this is pure numeric

Question

For instance:

\'1\'     => NG
\'243\'   => NG
\'1av\'   => OK
\'pRo\'   => OK
\'123k%\' => NG

I tried with

Answer 1

This should do the trick, without lookbehind:

^(\d*[a-zA-Z]\d*)+$