The CAS Registry Mumber 26402-29-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,6,4,0 and 2 respectively; the second part has 2 digits, 2 and 9 respectively. Calculate Digit Verification of CAS Registry Number 26402-29: (7*2)+(6*6)+(5*4)+(4*0)+(3*2)+(2*2)+(1*9)=89 89 % 10 = 9 So 26402-29-9 is a valid CAS Registry Number.