Question

I am a 9 letter word. My first four letters are a part of the body.
My last three letters are a number.
If you lose me, it’d be your worst nightmare.

Answer 1

Answer:

Cellphone

Explanation:

Cell is a body part and one is a number.

Answer 2

Answer:

Cellphone

Explanation:

First four letters part of the body:cell

last 3 letters is number one