Rhenium has one stable isotope which is rhenium-185. Rhenium that is found in nature is made up of of 37.4% rhenium-185 and 62.6% rhenium-187. Rhenium has 33 known radioisotopes. They range from rhenium-160 to rhenium-194. The longest-lived radioisotope of rhenium is rhenium-183 which have a half-life of 70 days.