The CAS Registry Mumber 91345-75-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,1,3,4 and 5 respectively; the second part has 2 digits, 7 and 5 respectively. Calculate Digit Verification of CAS Registry Number 91345-75: (7*9)+(6*1)+(5*3)+(4*4)+(3*5)+(2*7)+(1*5)=134 134 % 10 = 4 So 91345-75-4 is a valid CAS Registry Number.