The CAS Registry Mumber 2712-80-3 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,7,1 and 2 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 2712-80: (6*2)+(5*7)+(4*1)+(3*2)+(2*8)+(1*0)=73 73 % 10 = 3 So 2712-80-3 is a valid CAS Registry Number.