The CAS Registry Mumber 128637-95-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,8,6,3 and 7 respectively; the second part has 2 digits, 9 and 5 respectively. Calculate Digit Verification of CAS Registry Number 128637-95: (8*1)+(7*2)+(6*8)+(5*6)+(4*3)+(3*7)+(2*9)+(1*5)=156 156 % 10 = 6 So 128637-95-6 is a valid CAS Registry Number.