The CAS Registry Mumber 74417-97-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,4,1 and 7 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 74417-97: (7*7)+(6*4)+(5*4)+(4*1)+(3*7)+(2*9)+(1*7)=143 143 % 10 = 3 So 74417-97-3 is a valid CAS Registry Number.