An 11 sided polygon is a hendecagon and a 12 sided polygon is a dodecagon
The name of a 11 sided polygon is Hendecagon.
I suggest you forget about memorizing fancy names - which really serve no useful purpose - and just call them "20-sided polygon", "21-sided polygon", etc.
An icosikaidigon is a 22-sided polygon. For names of polygons see http://mathforum.org/dr.math/faq/faq.polygon.names.html
The name of a 51 sided polygon is Pentaconhenagon. The name of a 52 sided polygon is Pentacondigon. The name of a 53 sided polygon is Pentacontrigon. The name of a 54 sided polygon is Pentacontetragon. The name of a 55 sided polygon is Pentaconpentagon. The name of a 56 sided polygon is Pentaconheptagon. The name of a 57 sided polygon is Pentaconhexagon. The name of a 58 sided polygon is Pentaconoctagon. The name of a 59 sided polygon is Pentaconenneagon.
An 11 sided polygon is a hendecagon and a 12 sided polygon is a dodecagon
The name of a 11 sided polygon is Hendecagon.
I suggest you forget about memorizing fancy names - which really serve no useful purpose - and just call them "20-sided polygon", "21-sided polygon", etc.
The name of a polygon with 100 sides is a "hecatontagon," and a polygon with 1000 sides is called a "chiliagon." So, if you ever need to impress someone at a party with your knowledge of shapes, now you know what to call those bad boys.
A pentagon.
icosagon
Using systematic polygon names, a 91-sided polygon would be called an enneacontakaihenagon.
Using standardized polygon names, a 54-sided polygon would be called a pentacontakaitetragon.
The name of a fifteen sided polygon is known to have two names : pentakaidecagon, pentadecagon John Irving Dr. Math
icosikaidi is the name for a 22 sided polygon. For a list of the names for polygons, see the related link.
Applying systematic polygon names, a 75-sided regular polygon would be called a heptacontakaipentagon.
Expressed using systematic polygon names, an 83-sided regular polygon would be called an octacontakaitrigon.