One hundred, written 100 or spelled one hundred, is the natural integer immediately following 99 and preceding 101. It is the first three‑digit positive number in base ten and equals 10 squared (10×10). Because of its role as 10^2, 100 is a round, highly familiar quantity across counting systems and everyday measurement.

Mathematical characteristics

In arithmetic and number theory 100 is a composite number with prime factorization 2^2 × 5^2. Its positive divisors are 1, 2, 4, 5, 10, 20, 25, 50 and 100. It is a perfect square (10^2) and, with the sum of its proper divisors equal to 117, it is classified as an abundant number. In common numeral systems it appears as binary 1100100 and hexadecimal 0x64; in the ASCII table the decimal code 100 corresponds to the lowercase letter "d."

History and naming

The English word hundred derives from older Germanic forms ultimately related to the Proto‑Indo‑European root for numerous groups. In Latin the word centum means "a hundred," a root that survives in centi‑ (one hundredth) and century (a period of one hundred years). The Romans used the letter C as the conventional numeral for 100.

Uses and examples

  • Percentages: 100 percent denotes a whole or complete quantity and is the basis of the percent system (‰ and % are related units).
  • Currency and units: a cent is commonly one one‑hundredth of a basic monetary unit (for example, 100 cents = 1 dollar or 1 euro).
  • Science and measurement: on the Celsius temperature scale, the boiling point of water is defined as 100 °C at standard atmospheric pressure.
  • Sports and culture: scoring 100 runs in cricket is called a century; the 100‑metre sprint is a marquee athletics event.
  • Science: the chemical element with atomic number 100 is fermium, named after the physicist Enrico Fermi.

Notable facts and distinctions

The number 100 functions frequently as a threshold or milestone — from centennial anniversaries to exam grades where 100 often represents the maximum score. Its status as a square of the base (10) and a convenient round figure in the decimal system has made it a central reference point in measurement, accounting, and everyday language. For more technical or historical details see linked resources.

Contextual links: 99, natural number, 101, abundant, C.