The CAS Registry Mumber 91417-93-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,1,4,1 and 7 respectively; the second part has 2 digits, 9 and 3 respectively. Calculate Digit Verification of CAS Registry Number 91417-93: (7*9)+(6*1)+(5*4)+(4*1)+(3*7)+(2*9)+(1*3)=135 135 % 10 = 5 So 91417-93-5 is a valid CAS Registry Number.