The CAS Registry Mumber 108428-71-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,8,4,2 and 8 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 108428-71: (8*1)+(7*0)+(6*8)+(5*4)+(4*2)+(3*8)+(2*7)+(1*1)=123 123 % 10 = 3 So 108428-71-3 is a valid CAS Registry Number.