The CAS Registry Mumber 42233-08-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,2,2,3 and 3 respectively; the second part has 2 digits, 0 and 8 respectively. Calculate Digit Verification of CAS Registry Number 42233-08: (7*4)+(6*2)+(5*2)+(4*3)+(3*3)+(2*0)+(1*8)=79 79 % 10 = 9 So 42233-08-9 is a valid CAS Registry Number.