The CAS Registry Mumber 120105-59-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,0,1,0 and 5 respectively; the second part has 2 digits, 5 and 9 respectively. Calculate Digit Verification of CAS Registry Number 120105-59: (8*1)+(7*2)+(6*0)+(5*1)+(4*0)+(3*5)+(2*5)+(1*9)=61 61 % 10 = 1 So 120105-59-1 is a valid CAS Registry Number.