The compound Cu₂HPO₄ is called Copper(I) Hydrogen Phosphate. Here's how to break down the name:

* Cu₂: This indicates two copper ions (Cu⁺) are present. The Roman numeral "I" in parentheses specifies that copper has a +1 oxidation state.

* HPO₄: This is the hydrogen phosphate anion, with a -2 charge.

Therefore, the full name of the compound is Copper(I) Hydrogen Phosphate.