The CAS Registry Mumber 115538-45-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,5,5,3 and 8 respectively; the second part has 2 digits, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 115538-45: (8*1)+(7*1)+(6*5)+(5*5)+(4*3)+(3*8)+(2*4)+(1*5)=119 119 % 10 = 9 So 115538-45-9 is a valid CAS Registry Number.