I am trying to reproduce the results of a paper which looks at proton decay. I would like to convert the proton decay width (given in units of $\rm GeV$) to a lifetime in years. The formula is below:

   $\Gamma (p\to  \pi^0 \mu^+)_{\rm flipped}=
\frac{g_5^4m_p |V_{ud}|^2 |(U_l)_{21}|^2
}{32\pi M_X^4}(1-\frac{m_\pi^2}{m_p^2})^2
A_L^2 A_{S_1}^2 \left(\langle \pi^0\vert (ud)_Ru_L\vert
 p\rangle_{\mu}\right)^2$

Here $A_{L}=1.2$, $A_{S}=1.5$, $m_{\pi}=0.139$ GeV, $m_{p}=0.938$ GeV,
$\left(\langle \pi^0\vert (ud)_Ru_L\vert
 p\rangle_{\mu}\right) = -0.118 \rm{GeV}^2$, $|V_{ud}|^2\approx 0.97$. The lifetime ($\tau=1/\Gamma$ in natural units) formula derive from the one above  is 

$ \tau (p\to  \pi^0 \mu^+)_{\rm flipped}\simeq 
    9.7 \times 10^{35} \times  |(U_l)_{21}|^{-2}
    \biggl(\frac{M_X}{10^{16}~{\rm GeV}}\biggr)^4
     \biggl(\frac{0.0378}{\alpha_5}\biggr)^2 ~{\rm yrs}~.$

where $\alpha_{5}=\frac{g_{5}}{4\pi}$.  I have tried plugging in these numbers and then converting from GeV to years ($1\rm{GeV}=4.81851\times10^{16}$ year$^{-1}$). Not sure what I am doing wrong as I get far too small a lifetime. Help is appreciated.