g=ExampleData[{"NetworkGraph","ZacharyKarateClub"}]

VertexCount[g]

EdgeCount[g]

With[{d=DegreeCentrality[g]},Pick[VertexList[g],d,Max[d]]]

Part[VertexList[g],Reverse[Ordering[BetweennessCentrality[g]]][[;;2]]]

Pick[VertexList[g],DegreeCentrality[g],0 | 1]