The CAS Registry Mumber 82509-26-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,2,5,0 and 9 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 82509-26: (7*8)+(6*2)+(5*5)+(4*0)+(3*9)+(2*2)+(1*6)=130 130 % 10 = 0 So 82509-26-0 is a valid CAS Registry Number.