Is barium-123 stable or radioactive?

I learned to take the N/Z ratio to determine if a isotope is stable or radioactive. Generally, if the ratio is 1, the isotope is stable. However, as the M of the atom increases, the acceptable ratio vable of a stable isotope also increases ( from (1 alway the way to 1.52). So is Barium-123, a farly large isotope, stable with a ratio of 1.2 ?