The CAS Registry Mumber 128099-75-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,8,0,9 and 9 respectively; the second part has 2 digits, 7 and 5 respectively. Calculate Digit Verification of CAS Registry Number 128099-75: (8*1)+(7*2)+(6*8)+(5*0)+(4*9)+(3*9)+(2*7)+(1*5)=152 152 % 10 = 2 So 128099-75-2 is a valid CAS Registry Number.