The CAS Registry Mumber 131308-34-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,1,3,0 and 8 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 131308-34: (8*1)+(7*3)+(6*1)+(5*3)+(4*0)+(3*8)+(2*3)+(1*4)=84 84 % 10 = 4 So 131308-34-4 is a valid CAS Registry Number.