We present a 155ks NuSTAR observation of the $zsim2$ hot dust-obscured galaxy (hot DOG) W1835+4355. We extracted spectra from the two NuSTAR detectors and analyzed them jointly with the archival XMM PN and MOS spectra. We performed a spectroscopic analysis based on both phenomenological and physically motivated models employing toroidal and spherical geometry for the obscurer. In all the modelings, the source exhibits a Compton-thick column density $N_{rm H} gtrsim 10^{24}$ cm$^{-2}$, a 2-10 keV luminosity $L_{2-10}approx2times10^{45}$ erg s$^{-1}$ , and a prominent soft excess ($sim5-10$ % of the primary radiative output), which translates into a luminosity $sim10^{44}$ erg s$^{-1}$. We modeled the spectral energy distribution from 1.6 to 850 $mu m$ using a clumpy two-phase dusty torus model plus a modified blackbody to account for emission powered by star formation in the far-infrared. We employed several geometrical configurations consistent with those applied in the X-ray analysis. In all cases we obtained a bolometric luminosity $L_{rm bol}approx3-5times10^{47}$ erg s$^{-1}$, which confirms the hyperluminous nature of this active galactic nucleus. Finally, we estimate a prodigious star formation rate of $sim$3000 $M_{odot},yr^{-1}$, which is consistent with the rates inferred for $zapprox2-4$ hyperluminous type I quasars. The heavily obscured nature, together with $L_{rm bol}$, the ratio of X-ray to mid-infrared luminosity, the rest-frame optical morphology, and the host star formation rate are indicative of its evolutionary stage. We can interpret this as a late-stage merger event in the transitional, dust-enshrouded, evolutionary phase eventually leading to an optically bright AGN.
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