The CAS Registry Mumber 286850-80-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,8,6,8,5 and 0 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 286850-80: (8*2)+(7*8)+(6*6)+(5*8)+(4*5)+(3*0)+(2*8)+(1*0)=184 184 % 10 = 4 So 286850-80-4 is a valid CAS Registry Number.