Why do Platonists say that numbers do not exist in space and time?

In the philosophy of mathematics, Platonists define numbers as abstract objects that are nonspatiotemporal, nonphysical, and nonmental. They argue that numbers do not exist in space and time because they are not located anywhere in the physical universe and are not composed of physical matter.12

According to this view, because these objects lack physical extension and material substance, they are entirely noncausal, meaning they cannot enter into cause-and-effect relationships with other objects. Platonists maintain that numbers are real, objective entities that exist independently of human thought, similar to how the Moon exists independently of our ideas about it, but they differ from physical objects by existing outside the constraints of space and time. While some nontraditional versions of Platonism have attempted to assign spatiotemporal locations to mathematical objects to address epistemological concerns, the standard Platonist position remains that these structures are abstract and unchanging.123