We present the next-to-leading-order event-by-event EKRT model predictions for the centrality dependence of the charged hadron multiplicity in the pseudorapidity interval $|eta|le 0.5$, and for the centrality dependence of the charged hadron flow harmonics $v_n{2}$ obtained from 2-particle cumulants, in $sqrt{s_{NN}}=5.44$ TeV Xe+Xe collisions at the CERN Large Hadron Collider. Our prediction for the 0-5 % central charged multiplicity is $dN_{rm ch}/deta =1218pm 46$. We also predict $v_n{2}$ in Xe+Xe collisions to increase more slowly from central towards peripheral collisions than those in a Pb+Pb system. We find that at $10 dots 50$% centralities $v_2{2}$ is smaller and $v_3{2}$ is larger than in the Pb+Pb system while $v_4{2}$ is of the same magnitude in both systems. We also find that the ratio of flow harmonics in Xe+Xe collisions and in Pb+Pb collisions shows a slight sensitivity to the temperature dependence of the shear-viscosity-to-entropy ratio. As we discuss here, the new nuclear mass-number systematics especially in the flow harmonics serves as a welcome further constraint for describing the space-time evolution of a heavy-ion system and for determining the shear viscosity and other transport properties of strongly interacting matter.
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