The CAS Registry Mumber 72289-99-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,2,2,8 and 9 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 72289-99: (7*7)+(6*2)+(5*2)+(4*8)+(3*9)+(2*9)+(1*9)=157 157 % 10 = 7 So 72289-99-7 is a valid CAS Registry Number.