The CAS Registry Mumber 69303-80-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,9,3,0 and 3 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 69303-80: (7*6)+(6*9)+(5*3)+(4*0)+(3*3)+(2*8)+(1*0)=136 136 % 10 = 6 So 69303-80-6 is a valid CAS Registry Number.