The number of nitrogen molecules present in 1c.c of gas at NTP is

1 c.c = 1 mL. At NTP 1 mol of nitrogen gas occupy 22400 mL.

22400mL of ${\mathrm{N}}_2 \mathrm{gas} =6.023\times {10}^{23} \mathrm{molecules} \mathrm{of} {\mathrm{N}}_2$ 

$1 \mathrm{mL} \mathrm{of} {\mathrm{N}}_2 \mathrm{gas} =\frac{6.023\times {10}^{23} \mathrm{molecules}}{22400\mathrm{mL}}\times 1 \mathrm{mL}=2.69\times {10}^{19}\mathrm{molecules}$