What is the coordination number of sodium in ${\mathrm{Na}}_2\mathrm{O}?$

In ${\mathrm{Na}}_2\mathrm{O}$ there is antifluorite structure. Here negative  ions form the ccp arrangement so that each positive ion is surrounded by 4 negative ions and each negative ion is surrounded by 8 positive ions. So coordination no. of Na⁺ is 4.