The CAS Registry Mumber 123836-67-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,3,8,3 and 6 respectively; the second part has 2 digits, 6 and 7 respectively. Calculate Digit Verification of CAS Registry Number 123836-67: (8*1)+(7*2)+(6*3)+(5*8)+(4*3)+(3*6)+(2*6)+(1*7)=129 129 % 10 = 9 So 123836-67-9 is a valid CAS Registry Number.