The CAS Registry Mumber 28664-29-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,8,6,6 and 4 respectively; the second part has 2 digits, 2 and 9 respectively. Calculate Digit Verification of CAS Registry Number 28664-29: (7*2)+(6*8)+(5*6)+(4*6)+(3*4)+(2*2)+(1*9)=141 141 % 10 = 1 So 28664-29-1 is a valid CAS Registry Number.