Let capitalised letters of the alphabet stand for 4-digit prime numbers each of whose digits is distinct and also prime, so that e.g. A=5237.

A pair of such letters stands for the concatenation of two such numbers to form an 8-digit number, e.g. AA=52375237

Denote 8 different such 4-digit primes by the letters of the word CAPTURES, so that each of CP,ET,PU,RU,TE,TR, and UC is also prime.

Given that A=5237, what is the value of S?