Overview

The number eight is the natural number that follows seven and precedes nine. Written as 8 in the common Hindu–Arabic numeral system, it appears as VIII in Roman numerals. Eight is even, positive, and widely encountered in science, culture and everyday counting.

Mathematical properties

Eight is a composite number with divisors 1, 2, 4 and 8. Its prime factorization is 23, so it is the cube of two and the first nontrivial power of two after 1. In binary notation eight is written 1000 and in octal (base‑8) it is represented as 10. In computing, eight bits commonly form a byte or octet.

History and etymology

The English word "eight" derives from Old English eahta and further back to Proto‑Germanic and Proto‑Indo‑European roots. Numeric prefixes related to eight include octa‑ and octo‑ in Greek and Latin, used in terms such as "octagon" (an eight‑sided polygon). For basic numeral usage and symbols see numeral reference.

Occurrences and cultural significance

  • Oxygen has atomic number 8 in the periodic table, making it central to chemistry and life.
  • There are eight major planets in the Solar System under the current classification.
  • In music an octave spans eight diatonic notes; in ensembles an "octet" comprises eight performers.
  • The octagon shape (eight sides) is used for road signs and architectural motifs; the figure eight relates to looping forms and the infinity symbol rotated 90°.
  • In several cultures, notably Chinese, the number eight is associated with good fortune and prosperity.

Notable facts and distinctions

Eight is the first integer after one that is both a perfect cube (23) and a power of two. Its proper divisors sum to seven, so it is classified as a deficient number. Practical examples of eight appear in chess (an 8×8 board), timekeeping and labor history (the eight‑hour day concept), and many technical standards that group items in eights.

For further exploration of numeral systems and cultural uses of numbers, consult general references or specialized entries such as numerical systems and the Roman numeral overview at VIII.