Most players are familiar with general HCP guidelines such as :
Small Slams: 31-33 HCP
Grand Slams: 35-37 HCP
These are approximate and surely depend on distribution. At notrump, you usually need to be towards the high end of the ranges above (especially if both hands are balanced). With a long running suit, you might make 6NT with fewer HCP. For suit slams, you could easily get by on less than 31 HCP with lots of shape (voids, singletons, long suits).
Those HCP n
...
AQ9 
KQ952 
Q8 
A74