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
Using systematic polygon names, a 57-sided regular polygon would be called a pentacontakaiheptagon.
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.
A 100-sided polygon is called a Hectagon.A 1000-sided polygon is called a Chiliagon.
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.