The CAS Registry Mumber 129345-71-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,9,3,4 and 5 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 129345-71: (8*1)+(7*2)+(6*9)+(5*3)+(4*4)+(3*5)+(2*7)+(1*1)=137 137 % 10 = 7 So 129345-71-7 is a valid CAS Registry Number.