The CAS Registry Mumber 134283-99-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,4,2,8 and 3 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 134283-99: (8*1)+(7*3)+(6*4)+(5*2)+(4*8)+(3*3)+(2*9)+(1*9)=131 131 % 10 = 1 So 134283-99-1 is a valid CAS Registry Number.