The CAS Registry Mumber 103931-50-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,3,9,3 and 1 respectively; the second part has 2 digits, 5 and 0 respectively. Calculate Digit Verification of CAS Registry Number 103931-50: (8*1)+(7*0)+(6*3)+(5*9)+(4*3)+(3*1)+(2*5)+(1*0)=96 96 % 10 = 6 So 103931-50-6 is a valid CAS Registry Number.