A neutron outside the nucleus lives for about 15 minutes and decays mainly through weak decays (beta decay). Many other weakly decaying particles decay with lifetimes between $10^{-10}$ and $10^{-12}$ seconds, which is consistent with $\alpha\_W \simeq 10^{-6}$.

Why does the neutron lives so much longer than the others?
['https://physics.stackexchange.com/questions/31514', 'https://physics.stackexchange.com', 'https://physics.stackexchange.com/users/1502/']
You can estimate the neutron lifetime using dimensional analysis. Beta decay is correctly described by the well known four-fermion Fermi theory, so the amplitude must be proportional to the coupling $G\_F\approx10^{-5}\text{GeV}^{-2}$ (the Fermi constant). The decay rate is proportional to the squared amplitude:

$$\Gamma\propto G\_F^2\thinspace.$$

$\Gamma$ has units of Mass while $G\_F^2$ has units of $[\text{Mass}]^{-4}$, so to get the units wright we must have

$$\Gamma\propto G\_F^2 \Delta^5$$

where $\Delta$ is some quantity that has units of mass. The relevant mass scale in neutron decay is the mass difference between neutron and proton, so $\Delta=m\_n-m\_p\approx10^{-3}\text{GeV}$. 

To be a bitsy more accurate one can try guess the $\pi$ dependence of the decay rate. This comes from the phase space of a 3-body decay, which usually goes as 

$$(2\pi)^4\times\Big[\thinspace(2\pi)^{-3}\times(2\pi)^{-3}\times(2\pi)^{-3}\Big]\times (\pi^2)\ \propto\ \pi^{-3}\thinspace.$$

The first factor comes from the four momenta conservation delta function, the three $(2\pi)^{-3}$ in the bracket come from the integration measure of the 4-momenta of each outgoing particle and the last factor comes from integrating the angle variables. One finally gets the following estimation

$$\Gamma\propto \frac{1}{\pi^3}G\_F^2(m\_n-m\_p)^5$$

If one plugs in all the numbers, the estimated lifetime of the neutron reads

$$\tau\_{\text{neutron}}\ =\ \Gamma^{-1}\ \approx\ \pi^3 \ \text{sec.}$$

This is a bit shorter than the real value which is at least one order of magnitude larger. But it explains why the neutron's lifetime is so large (inverse of the 5th power of the small mass difference) with respect to other weak decay processes.
As you correctly state, the neutron decay is an decay due to the weak interaction, these are quite a bit slower than other decays due the mass of the
intermediate W boson, 81GeV, which slows the reaction, additionally the neutron decay only liberates a small amount of energy, around 1 MeV, it is the ratio of the liberated energy to the mass of the W which sets the speed of the reaction which is thus much slower than other decays as all the other particle decay release much more energy.