If your intention is to sell to another domainer, it could be tough. Domainers are very picky about domain metrics, when they pay premium to another domainer.
For an "end-user", numbers are fine if used as a substitute for the words "for (4)" or "to (2)" sandwiched between keywords. It makes the domain more catchy or brandable. Numbers at the front are a hard sell, though. People are not accustomed to typing domains starting with a number.
If you are scared that you might lose out for the exact word match "for" in search engines, i found out that you can easily compensate by spelling it out on the webpage title and Google will still match it. For example, if your domain is food4life, then you add a webpage title "food for life". Google will still match all three words and you still get propelled to the top. I have some domains like that so this is just based on my experience.