It's quite acceptable to call it a 1,000,000-agon but what's more important is knowing how to work out its properties.
name of 4000 sided polygon
The name of a 200 sided polygon is dihectagon.
The name of a 600 sided polygon is Hexcosiagon.
there is no such thing as two-sided polygon.
The name of a sided polygon is Octaconpentagon.
A one-million-sided polygon.
Hecatommyriagon
It is called megagon, its internal angle's sum is 179999640 degrees (that a lot!)
The name of a 12 sided polygon is Dodecagon.
name of 4000 sided polygon
A 8 sided polygon is called a octagon.
The name of a 10 sided polygon is Decagon.
The name of a 19 sided polygon is enneadecagon.
The name of a 9 sided polygon is Nonagon.
The name of a 15 sided polygon is Pentadecagon.
The name of a 7 sided polygon is Heptagon.
The name of a 17 sided polygon is Heptadecagon.