Natural numbers only have integers not less than 0 (that is, 0 and positive integers), so there are countless natural numbers, usually represented by n.

Historically, there have been two views on whether 0 is a natural number in mathematics circles at home and abroad: one thinks that 0 is a natural number, and the other thinks that 0 is not a natural number. Since the founding of the People's Republic of China, textbooks for primary and secondary schools in China have always stipulated that natural numbers do not include 0. Most foreign mathematicians stipulate that 0 is a natural number.

Natural numbers start from 0, one by one, forming an infinite group.