The CAS Registry Mumber 42264-11-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,2,2,6 and 4 respectively; the second part has 2 digits, 1 and 1 respectively. Calculate Digit Verification of CAS Registry Number 42264-11: (7*4)+(6*2)+(5*2)+(4*6)+(3*4)+(2*1)+(1*1)=89 89 % 10 = 9 So 42264-11-9 is a valid CAS Registry Number.