The CAS Registry Mumber 120116-65-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,0,1,1 and 6 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 120116-65: (8*1)+(7*2)+(6*0)+(5*1)+(4*1)+(3*6)+(2*6)+(1*5)=66 66 % 10 = 6 So 120116-65-6 is a valid CAS Registry Number.