Toner, developer, image forming apparatus, and process cartridge

A toner, comprising:

• a base particle;
• and
• an external additive covering the base particle,
• wherein the toner includes a tetrahydrofuran-insoluble component
• wherein the tetrahydrofuran-insoluble component is heated for a first time from −80° C. to 150° C., cooled from 150° C. to −80° C., and then heated for a second time, the tetrahydrofuran-insoluble component having a glass transition temperature determined from a DSC curve when heated for the second time of from −50° C. to 10° C. and an average circularity not greater than 0.98, and satisfies the following relation:
• Bt−0.025×Ct≦1.80
• wherein Bt represents a BET specific surface area [m2/g] of the base particles having the external additives;
• and
• Ct represents a surface area coverage [%] of the external additive covering the base particle, which is a surface area ratio of the external additive to the surface area of the toner to which the external additive is attached,
• wherein the toner satisfies the following relation in an environment of 32° C. and 40% RH when a load reaches 3.00×10−4N at a load speed of 3.0 10−5N/sec:
• X/Dn≦0.14
• wherein X represents an average of deformation quantity [μm];
• and Dn represents a number-average particle diameter [μm].