A number is a mathematical object used for counting, measuring, and labeling.
Numbers are the foundation of mathematics. Types include natural numbers (1, 2, 3...), whole numbers (0, 1, 2...), integers (..., -2, -1, 0, 1, 2...), rational numbers (fractions), irrational numbers (π, √2), real numbers (all of the above), and complex numbers (a + bi). Numbers are represented using numeral systems like decimal, binary, and hexadecimal.
Numbers have been used since prehistoric times through tally marks. The first written numeral systems emerged in Sumer (3400 BCE) and Egypt (3200 BCE). The concept of zero was a revolutionary development in India around the 5th century CE. The real number system was formalized in the 19th century by Dedekind and Cantor.