The CAS Registry Mumber 128407-15-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,8,4,0 and 7 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 128407-15: (8*1)+(7*2)+(6*8)+(5*4)+(4*0)+(3*7)+(2*1)+(1*5)=118 118 % 10 = 8 So 128407-15-8 is a valid CAS Registry Number.