Is there any way to find a number N if it's Carmichael function is given.

Question

I know to find the Carmichael function [ C() ] of a given no. But I want to know if there is any method or shortcut to find a number N if it's C() is given.

Answer 1

PARI/GP examples:

n-Carmichael <=> B(n)=eulerphi(n),

where B(n)=PRODUCT(p: p-1|n-1, where p|n and p-Prime)

It's analog for: n-Prime<=> n-1=eulerphi(n)

Your method: n-Carmichael <=> C(n)|n-1

where: C(n)=znstar(n)[2][1]