As far as I can see the prefix is *not* sufficient, a single non-digit character...

masklinn on May 4, 2015 | parent | context | favorite | on: PHP: md5('240610708') == md5('QNKCDZO')

As far as I can see the prefix is not sufficient, a single non-digit character in the tail fails the conversion (and the equality check): http://3v4l.org/ctASF (vs http://3v4l.org/5FvJu, exact same strings but for the last character replaced by a digit)