The CAS Registry Mumber 129297-42-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,9,2,9 and 7 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 129297-42: (8*1)+(7*2)+(6*9)+(5*2)+(4*9)+(3*7)+(2*4)+(1*2)=153 153 % 10 = 3 So 129297-42-3 is a valid CAS Registry Number.