The CAS Registry Mumber 123528-52-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,3,5,2 and 8 respectively; the second part has 2 digits, 5 and 2 respectively. Calculate Digit Verification of CAS Registry Number 123528-52: (8*1)+(7*2)+(6*3)+(5*5)+(4*2)+(3*8)+(2*5)+(1*2)=109 109 % 10 = 9 So 123528-52-9 is a valid CAS Registry Number.