AB is the #CD prime and BA is the #DC prime.
It is the only existing reversal like that!
Find A, B, C, D.

In the above problem MN denotes a two-digit number i.e. 10*M+N.

37 is the 12th prime and 73 is the 21st prime 
             A=3,        B=7,        C=1,        D=2


Ecin reversals in other bases (where MN denotes a two-digit base r number, i.e., r*M+N, [AB and BA] and where the two-digit ordinal numbers [CD and DC] are decimal):

base 14: 9D is the 34th prime [139]
       and D9 is the 43rd prime [191]
             A=9,        B=D (13), C=3,        D=4
base 23: BG is the 57th prime [269]
       and GB is the 75th prime [379]
             A=B (11), B=G (16), C=5,        D=7
base 30: 11 is the 11th prime  [31]
             A=1,        B=1,        C=1,        D=1

 

Edited on March 18, 2013, 12:07 pm

Posted by Dej Mar on 2013-03-18 09:15:41