In this discussion, number refers to a counting number: [beautiful math coming... please be patient] $\,1\,$, $\,2\,$, $\,3\,$, and so on.
The factors of a number are the numbers that go into it evenly.
For example, the factors of
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$\,10\,$ are $\,1\,$, $\,2\,$, $\,5\,$, and $\,10\,$.
The factors of
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$\,42\,$ are $\,1\,$, $\,2\,$, $\,3\,$, $\,6\,$, $\,7\,$, $\,14\,$, $\,21\,$, and $\,42\,$.
Notice that factors occur in pairs:
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$1\times 42 = 42$
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$2\times 21 = 42$
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$3\times 14 = 42$
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$6\times 7 = 42$
Every number has a factor of
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$\,1\,$, because $\,1\,$ goes into everything evenly.
Also, every number has itself as a factor.
Thus, the number
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$\,1\,$ has only one factoritself.
Every other number has at least two factorsitself and $\,1\,$.