The CAS Registry Mumber 80077-18-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,0,7 and 7 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 80077-18: (7*8)+(6*0)+(5*0)+(4*7)+(3*7)+(2*1)+(1*8)=115 115 % 10 = 5 So 80077-18-5 is a valid CAS Registry Number.