This paper examines the syntax of additive compound numerals in Modern Standard Arabic (MSA), uncovering their unique properties related to number morphology, definiteness, and Case assignment within numeral–noun constructions. These properties necessitate a constituency analysis which reveals that compound numerals have the structure of copulative compounds in MSA, and they are phrases, not functional heads. Drawing on the distinction between inherent, lexical, and structural Cases, this paper posits that the accusative Case on the numerals is an inherent Case, inaccessible to syntactic transformations. Furthermore, the analysis of numeral–noun constructions as numerically quantified phrases (NQPs) explains the assignment of a structural accusative Case or the inherent genitive Case on the quantified noun, based on the overtness of NQ0. Finally, the paper addresses the intriguing question of how NQPs in MSA, despite lacking a nominative Case, can assume the subject position and govern agreement in both verbal and verbless sentences.