9 is the natural number following 8 and preceding 10.
In more detail:
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Natural Number: 9 belongs to the set of natural numbers (also known as counting numbers), which starts from 1 and extends infinitely.
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Integer: It is also an integer, which includes all whole numbers and their negatives.
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Real Number: 9 is a real number, encompassing all rational and irrational numbers.
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Odd Number: 9 is an odd number because it is not divisible by 2 without a remainder.
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Composite Number: 9 is a composite number because it has factors other than 1 and itself (specifically, 3). The factors of 9 are 1, 3, and 9.
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Perfect Square: 9 is a perfect square because it's the result of squaring an integer (3 x 3 = 9).
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Sum of Odd Numbers: As the reference noted, 9 is the sum of the first three odd numbers (1 + 3 + 5 = 9).
