The CAS Registry Mumber 80477-81-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,4,7 and 7 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 80477-81: (7*8)+(6*0)+(5*4)+(4*7)+(3*7)+(2*8)+(1*1)=142 142 % 10 = 2 So 80477-81-2 is a valid CAS Registry Number.