The CAS Registry Mumber 75129-34-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,1,2 and 9 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 75129-34: (7*7)+(6*5)+(5*1)+(4*2)+(3*9)+(2*3)+(1*4)=129 129 % 10 = 9 So 75129-34-9 is a valid CAS Registry Number.