The CAS Registry Mumber 5066-17-1 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,0,6 and 6 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 5066-17: (6*5)+(5*0)+(4*6)+(3*6)+(2*1)+(1*7)=81 81 % 10 = 1 So 5066-17-1 is a valid CAS Registry Number.