The CAS Registry Mumber 26328-87-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,6,3,2 and 8 respectively; the second part has 2 digits, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 26328-87: (7*2)+(6*6)+(5*3)+(4*2)+(3*8)+(2*8)+(1*7)=120 120 % 10 = 0 So 26328-87-0 is a valid CAS Registry Number.