The CAS Registry Mumber 108330-77-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,8,3,3 and 0 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 108330-77: (8*1)+(7*0)+(6*8)+(5*3)+(4*3)+(3*0)+(2*7)+(1*7)=104 104 % 10 = 4 So 108330-77-4 is a valid CAS Registry Number.