Stable 74Ge is the most common isotope, having a natural abundance of approximately 36%.
[5] At least 27 radioisotopes have also been synthesized ranging in atomic mass from 58 to 89.
(See gallium-68 generator for notes on the source of this isotope, and its medical use.)
The least stable known germanium isotope is 59Ge with a half-life of 13.3 ms.
[5] 76Ge is used in experiments on the nature of neutrinos, by searching for neutrinoless double beta decay.