The CAS Registry Mumber 126397-26-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,6,3,9 and 7 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 126397-26: (8*1)+(7*2)+(6*6)+(5*3)+(4*9)+(3*7)+(2*2)+(1*6)=140 140 % 10 = 0 So 126397-26-0 is a valid CAS Registry Number.