The CAS Registry Mumber 83767-43-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,3,7,6 and 7 respectively; the second part has 2 digits, 4 and 3 respectively. Calculate Digit Verification of CAS Registry Number 83767-43: (7*8)+(6*3)+(5*7)+(4*6)+(3*7)+(2*4)+(1*3)=165 165 % 10 = 5 So 83767-43-5 is a valid CAS Registry Number.