* A number: 402 is just a quantity, not a substance. It doesn't tell us what kind of atoms we're talking about.
* A chemical formula: If "402" represents a chemical formula, we need to know what the formula is to determine the number of atoms. For example, H₂O (water) has 3 atoms (2 hydrogen and 1 oxygen).
* A mass: If "402" refers to a mass (like 402 grams), we need to know the substance to calculate the number of atoms. The number of atoms in a given mass depends on the element's atomic mass.
To figure out the number of atoms, you need to provide more information.
