The CAS Registry Mumber 67205-84-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,7,2,0 and 5 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 67205-84: (7*6)+(6*7)+(5*2)+(4*0)+(3*5)+(2*8)+(1*4)=129 129 % 10 = 9 So 67205-84-9 is a valid CAS Registry Number.