The CAS Registry Mumber 130688-18-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,0,6,8 and 8 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 130688-18: (8*1)+(7*3)+(6*0)+(5*6)+(4*8)+(3*8)+(2*1)+(1*8)=125 125 % 10 = 5 So 130688-18-5 is a valid CAS Registry Number.