The CAS Registry Mumber 72880-97-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,2,8,8 and 0 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 72880-97: (7*7)+(6*2)+(5*8)+(4*8)+(3*0)+(2*9)+(1*7)=158 158 % 10 = 8 So 72880-97-8 is a valid CAS Registry Number.