Combined measurements of the Higgs boson mass, as well its production cross sections and branching fractions, are performed using the $H \to \gamma\gamma$ and $H \to ZZ^{*} \to 4l$ decay channels. The measurements are based on 36.1 fb$^{−1}$ of proton-proton collision data recorded by the ATLAS experiment at the LHC at $\sqrt{s}=$13 TeV. The Higgs boson mass is measured to be 124.98 $\pm$ 0.19 (stat) $\pm$ 0.21 (syst) GeV. The rates for gluon fusion, vector-boson fusion, $VH$, and $ttH$ production, as well as kinematic subdivisions of these processes, are found to be compatible with the Standard Model. The measured ratios of the Higgs boson couplings to their SM predictions are also consistent with the predictions.