The CAS Registry Mumber 88767-18-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,8,7,6 and 7 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 88767-18: (7*8)+(6*8)+(5*7)+(4*6)+(3*7)+(2*1)+(1*8)=194 194 % 10 = 4 So 88767-18-4 is a valid CAS Registry Number.