Try the following and see if it avoids all numbers:
Code:
// v.1.8.7
if (!eregi("[0-9]",$key) and strlen($key) > SMALL_WORDS_SIZE and strlen($key) <= MAX_WORDS_SIZE and !isset($common_words[$key]) and ereg('^['.$phpdig_words_chars[PHPDIG_ENCODING].'#$]',$key))
// v.1.8.8 RC1
if (!mb_eregi("[0-9]",$key) and mb_strlen($key) > SMALL_WORDS_SIZE and mb_strlen($key) <= MAX_WORDS_SIZE and !isset($common_words[$key]))