The CAS Registry Mumber 30820-38-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,0,8,2 and 0 respectively; the second part has 2 digits, 3 and 8 respectively. Calculate Digit Verification of CAS Registry Number 30820-38: (7*3)+(6*0)+(5*8)+(4*2)+(3*0)+(2*3)+(1*8)=83 83 % 10 = 3 So 30820-38-3 is a valid CAS Registry Number.