Slightly better would be:
Code:
(\d{0,3}[,]?\d{1,3} [Ww]ords)
That should get any number up to 6 digits with or without the comma. But, it would miss the first digit in 1000000.
If I hadn't see your solution, I think I would have suggested:
Which would pickup ", words". So, slightly safer is:
Code:
([\d,]{2,} [Ww]ords\b)