The mass displayed, \( 1.67 \times 10^{-21} \) grams, represents the mass of 1,000 protons.
To express this in the requested format \( 1.67 \times ___ \) grams, you can rewrite it as:
\( 1.67 \times 10^{-21} \) grams.
So, the answer is:
1.67 x 10^-21 grams.