An agency through whom I apply for a job are asking for the last 4 digits of my passport number?

Seems a little odd? What does everyone think? normal?

Never heard of this before, why not just ask them what they need it for?

Maybe they use it as some sort of initial password or security code for accessing something later, because they know if they ask you to make something up you'll just forget it.

I did a search on the internet, it seems the last 4 digits can be used to verify you say who you are?

Interesting, could you provide the link?