The CAS Registry Mumber 84054-99-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,0,5 and 4 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 84054-99: (7*8)+(6*4)+(5*0)+(4*5)+(3*4)+(2*9)+(1*9)=139 139 % 10 = 9 So 84054-99-9 is a valid CAS Registry Number.