The CAS Registry Mumber 87449-81-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,4,4 and 9 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 87449-81: (7*8)+(6*7)+(5*4)+(4*4)+(3*9)+(2*8)+(1*1)=178 178 % 10 = 8 So 87449-81-8 is a valid CAS Registry Number.