The CAS Registry Mumber 160909-86-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,6,0,9,0 and 9 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 160909-86: (8*1)+(7*6)+(6*0)+(5*9)+(4*0)+(3*9)+(2*8)+(1*6)=144 144 % 10 = 4 So 160909-86-4 is a valid CAS Registry Number.