What is the total number of atoms in the compound 4HNO3?

The compound 4HNO3 consists of 4 moles of nitric acid (HNO3). Each molecule of HNO3 contains 5 atoms (1 nitrogen and 3 oxygen atoms). Therefore, the total number of atoms in 4HNO3 is 4 moles * 5 atoms/mole = 20 atoms.