The CAS Registry Mumber 35406-99-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,5,4,0 and 6 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 35406-99: (7*3)+(6*5)+(5*4)+(4*0)+(3*6)+(2*9)+(1*9)=116 116 % 10 = 6 So 35406-99-6 is a valid CAS Registry Number.