Which isotope of plutonium is one of the three primary fissile isotopes, the other two being uranium-233 and uranium-235?

Plutonium is a radioactive actinide metal whose isotope, plutonium-239, is one of the three primary fissile isotopes. To be considered fissile, an isotope's atomic nucleus must be able to break apart or fission when struck by a slow moving neutron and to release enough additional neutrons to sustain the nuclear chain reaction by splitting further nuclei. Fission of a kilogram of plutonium-239 can produce an explosion equivalent to 21, 000 tons of TNT. It is this energy that makes plutonium-239 useful in nuclear weapons and reactors.