Prime
From ACT Wiki
1. Credit rating.
The strongest credit ratings for shorter term obligations.
Prime represents the strongest credit ratings, for the safest investments.
2.
More generally, highly creditworthy.
3.
More broadly still, the highest quality, however evaluated.
For example, an equity share that is considered to be of the highest quality. Also called 'blue chip'.
4. Encryption.
Abbreviation for prime number.