Control radix in which numbers are printed and printing of the radix
See set-print-base and set-print-radix for detailed
discussions of those functions.
Here is a sample log.
ACL2 !>(list 25 25/3) (25 25/3) ACL2 !>(set-print-base-radix 16 state) <state> ACL2 !>(list 25 25/3) (#x19 #x19/3) ACL2 !>(set-print-base-radix 10 state) <state> ACL2 !>(list 25 25/3) (25 25/3) ACL2 !>