For the reversible reaction $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$ at $500^\circ \text{C}$, the value of $K_p$ is $1.44 \times 10^{-5}$ when partial pressure is measured in atmosphere. The corresponding value of $K_c$, with concentration in mole litre$^{-1}$, is