The CAS Registry Mumber 138505-01-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,8,5,0 and 5 respectively; the second part has 2 digits, 0 and 1 respectively. Calculate Digit Verification of CAS Registry Number 138505-01: (8*1)+(7*3)+(6*8)+(5*5)+(4*0)+(3*5)+(2*0)+(1*1)=118 118 % 10 = 8 So 138505-01-8 is a valid CAS Registry Number.