"Round number" is specifically an ambiguous terminology though. You could use "integer" instead, but it's really more to do with the concept of significant figures. e.g. 129 is an integer, but 130 is a "rounder number" than 129 and 100 is rounder still. To make it more confusing, decimal numbers ending in 5 (before the zeros) are often considered round, 150 is rounder than 130.

However, mathematically there's a totally different definition: A round number is a number that is the product of a considerable number of comparatively small factors. That means that 24 is rounder than 25.