Tridecagon (or triskaidecagon).
Check out a list that includes the first 20 at the University of Regina Related Link, below.
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a 4 sided shape is called a quadrilateral
== == A 56 sided shape is called a Pentacontakaihexagon.
A 600-sided shape is a hexcosiagon.
A twelve sided shape is a dodecagon.
A 2d nine sided shape is called a nonagon.