The CAS Registry Mumber 40797-41-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,0,7,9 and 7 respectively; the second part has 2 digits, 4 and 1 respectively. Calculate Digit Verification of CAS Registry Number 40797-41: (7*4)+(6*0)+(5*7)+(4*9)+(3*7)+(2*4)+(1*1)=129 129 % 10 = 9 So 40797-41-9 is a valid CAS Registry Number.