The CAS Registry Mumber 184686-99-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,8,4,6,8 and 6 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 184686-99: (8*1)+(7*8)+(6*4)+(5*6)+(4*8)+(3*6)+(2*9)+(1*9)=195 195 % 10 = 5 So 184686-99-5 is a valid CAS Registry Number.