The CAS Registry Mumber 91487-11-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,1,4,8 and 7 respectively; the second part has 2 digits, 1 and 1 respectively. Calculate Digit Verification of CAS Registry Number 91487-11: (7*9)+(6*1)+(5*4)+(4*8)+(3*7)+(2*1)+(1*1)=145 145 % 10 = 5 So 91487-11-5 is a valid CAS Registry Number.