Yes, NAUTILI is a Scrabble word!

Letter values in Scrabble US: N 1, A 1, U 1, T 1, I 1, L 1, I 1.

Is it a valid word?

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

a submarine that is propelled by nuclear power
cephalopod mollusk of warm seas whose females have delicate papery spiral shells
cephalopod of the Indian and Pacific oceans having a spiral shell with pale pearly partitions

Also: nuclear submarine, nuclear-powered submarine, paper nautilus, argonauta argo, chambered nautilus, pearly nautilus.