Why infinity is a largest natural number?

Answer 1

Actually, infinity is not a natural number. It is simply a concept of having no upper bound. However, it is possible to have and compare different infinities. For example, we use aleph_0 to represent the cardinality (size) of the set of natural numbers. The cardinality of the set of integers, rational numbers, gaussian integers all have the same cardinality of aleph_0. The set of real numbers has cardinality aleph_1, which is greater than aleph_0. It is possible to create a sequence of increasing infinities (aleph_2, aleph_3, ...), which are called transfinite numbers.