what is the benefit of lcm in cryptography? what is the benefit of lcm in cryptography?
and what is the effect of lcm on public key?

note *
lcm = Least common multiple

thanks
Regarding public key: In two prime RSA you often compute the secret key from the public as $d=e^{-1} \pmod {(p-1)(q-1)},\;$ but using $d=e^{-1} \pmod {\mathrm{lcm}(p-1,q-1)}$ may have some advantages.