In the novel Dune, ‘Mentats’ are humans trained to mimic computers: human minds developed to staggering heights of cognitive and analytical ability.
With this in mind, you may be able to guess what’s in store at the Mentat Wiki, which calls itself “a collaborative environment for exploring ways to become a better thinker”:
‘Mental Math’ teaches you how to cube and cube-root numbers in your head (and fifth roots), while one memory technique presented teaches you to hold a perpetual calendar in your head (what day did/will a certain date fall on?).
Certainly gets those brain cells working again.