The CAS Registry Mumber 87289-88-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,2,8 and 9 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 87289-88: (7*8)+(6*7)+(5*2)+(4*8)+(3*9)+(2*8)+(1*8)=191 191 % 10 = 1 So 87289-88-1 is a valid CAS Registry Number.