The CAS Registry Mumber 313666-93-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 3,1,3,6,6 and 6 respectively; the second part has 2 digits, 9 and 3 respectively. Calculate Digit Verification of CAS Registry Number 313666-93: (8*3)+(7*1)+(6*3)+(5*6)+(4*6)+(3*6)+(2*9)+(1*3)=142 142 % 10 = 2 So 313666-93-2 is a valid CAS Registry Number.