1.
It is the only one that is neither prime nor composite.
It is the only one whose square (cube, higher powers) is the same as itself.
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The numbers that belong to the series are the following: 1, 2, 5, 10, 13, 26, 29 and 48.
30
8
133 ,because all haveroot squares except 133
1 - it is the only number that is neither prime nor composite.