T=21 icosahedral capsid
The capsid is composed 60 asymmetric units made of 21 proteins (T=21), for a total of 1260 capsid proteins. These capsids are skewed, and are therefore described as either right- (dextro) or left- (laevo) handed.
Icosahedric triangulation number is calculated following Caspar and Klug system
D. L. Caspar, A. Klug
Cold Spring Harb. Symp. Quant. Biol. 1962; 27: 1?24