# Why does Neptunium-236 have such a long half-life?

Neptunium-236 has a half-life of about 154,000 years, which is quite long for an isotope with odd numbers of both protons an neutrons, correct?

Other 'odd-odd' nuclides with longer-than-expected half-lifes can only decay by going through major changes in spin, so are considered 'high-spin stabilized'. But I cannot find a place where it specifically says this about Np-236......

The quantity $$Z^2/A$$ equals 36.6 for this isotope, which makes it not have any significant probability of decay by spontaneous fission. See https://en.wikipedia.org/wiki/Spontaneous_fission .
In alpha decay, its daughter will also be odd-odd, so the alpha decay half-life doesn't get shorter just because it's odd-odd. Its $$Z$$ isn't very high, so it's not surprising that alpha decay is weak.