The CAS Registry Mumber 135488-80-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,5,4,8 and 8 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 135488-80: (8*1)+(7*3)+(6*5)+(5*4)+(4*8)+(3*8)+(2*8)+(1*0)=151 151 % 10 = 1 So 135488-80-1 is a valid CAS Registry Number.