The CAS Registry Mumber 709031-34-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 7,0,9,0,3 and 1 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 709031-34: (8*7)+(7*0)+(6*9)+(5*0)+(4*3)+(3*1)+(2*3)+(1*4)=135 135 % 10 = 5 So 709031-34-5 is a valid CAS Registry Number.