The CAS Registry Mumber 13280-85-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,3,2,8 and 0 respectively; the second part has 2 digits, 8 and 5 respectively. Calculate Digit Verification of CAS Registry Number 13280-85: (7*1)+(6*3)+(5*2)+(4*8)+(3*0)+(2*8)+(1*5)=88 88 % 10 = 8 So 13280-85-8 is a valid CAS Registry Number.