The CAS Registry Mumber 459-16-5 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 4,5 and 9 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 459-16: (5*4)+(4*5)+(3*9)+(2*1)+(1*6)=75 75 % 10 = 5 So 459-16-5 is a valid CAS Registry Number.