Physicist Richard Feynman did not predict a specific highest atomic number conceivable on the periodic table. However, he did provide insights on the general trends and limitations of the periodic table.
In his lectures and writings, Feynman discussed the concept of the "island of stability" regarding superheavy elements. He speculated that there might be a region of relatively stable isotopes for elements with very high atomic numbers, which could potentially exist beyond the currently known elements. Feynman suggested that this island of stability might occur around atomic numbers 114, 120, or even higher.
While Feynman's ideas and contributions to physics are highly regarded, the actual discovery and understanding of superheavy elements have progressed significantly since his time. The current highest atomic number on the periodic table is oganesson (element 118), which was officially recognized in 2016. Research in this area is ongoing, and scientists continue to explore the possibilities and properties of elements with even higher atomic numbers.