The CAS Registry Mumber 128230-97-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,8,2,3 and 0 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 128230-97: (8*1)+(7*2)+(6*8)+(5*2)+(4*3)+(3*0)+(2*9)+(1*7)=117 117 % 10 = 7 So 128230-97-7 is a valid CAS Registry Number.