How many pictures should an art portfolio contain?

Question:

How many pictures should an art portfolio contain?

i'm trying to come up with a portfolio of my artwork to apply for a Job, and i don't know how many pieces of artwork i should show them, or put in it.
They want a Digital portfolio, as in through e-mail, and it's a big time company, so i'm sure it's safe, and plus, i'll still have the original copy. so yeah. how many pieces of work. and i guess as a side question, is it safe to do?

Best Answer - Chosen by Asker:

As many that show them you can do art well.