- published: 10 May 2011
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100 (one hundred) (Roman numeral C, reinforced by Latin centum) is the natural number following 99 and preceding 101.
One hundred is the square of 10 (in scientific notation it is written as 102). The standard SI prefix for a hundred is "hecto-".
One hundred is the basis of percentages (per cent meaning "per hundred" in Latin), with 100% being a full amount.
It is the sum of the first nine prime numbers, as well as the sum of four pairs of prime numbers (47 + 53, 17 + 83, 3 + 97, 41 + 59), and the sum of the cubes of the first four integers (100 = 13 + 23 + 33 + 43). Also, 26 + 62 = 100, thus 100 is a Leyland number.
One hundred is also an 18-gonal number. It is divisible by the number of primes below it, 25 in this case. But it can not be expressed as the difference between any integer and the total of coprimes below it, making it a noncototient. However, it can be expressed as a sum of some of its divisors, making it a semiperfect number.
100 is a Harshad number in base 10, and also in base 4, and in that base it is a self-descriptive number.
Year 100 (C) was a leap year starting on Wednesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Traianus and Frontinus (or, less frequently, year 853 Ab urbe condita). The denomination 100 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
A number is a mathematical object used to count and measure. In mathematics, the definition of number has been extended over the years to include such numbers as zero, negative numbers, rational numbers, irrational numbers, and complex numbers.
Mathematical operations are certain procedures that take one or more numbers as input and produce a number as output. Unary operations take a single input number and produce a single output number. For example, the successor operation adds one to an integer, thus the successor of 4 is 5. Binary operations take two input numbers and produce a single output number. Examples of binary operations include addition, subtraction, multiplication, division, and exponentiation. The study of numerical operations is called arithmetic.
A notational symbol that represents a number is called a numeral. In addition to their use in counting and measuring, numerals are often used for labels (telephone numbers), for ordering (serial numbers), and for codes (e.g., ISBNs).