Write 128 as a product of primes

2 x 2 x 2 x 2 x 2 x 2 x 2 = 128

OR

2^7

Step-by-step explanation:

2 is the only prime number you can multiply to get 128.

as such your answers are:

2^7

or

2 x 2 x 2 x 2 x 2 x 2 x 2.

(if you don't know yet, 2^7 is just a simple way to say 2 times itself 7 times.)