The CAS Registry Mumber 97538-43-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,7,5,3 and 8 respectively; the second part has 2 digits, 4 and 3 respectively. Calculate Digit Verification of CAS Registry Number 97538-43: (7*9)+(6*7)+(5*5)+(4*3)+(3*8)+(2*4)+(1*3)=177 177 % 10 = 7 So 97538-43-7 is a valid CAS Registry Number.