Yes, PAPAYA is a Scrabble word!

Letter values in Scrabble US: P 3, A 1, P 3, A 1, Y 4, A 1.

Is it a valid word?

PAPAYA is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

tropical American shrub or small tree having huge deeply palmately cleft leaves and large oblong yellow fruit
large oval melon-like tropical fruit with yellowish flesh

Also: papaya tree, melon tree, carica papaya.

Not playable in Scrabble US: PAPAIA.