The CAS Registry Mumber 87308-16-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,3,0 and 8 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 87308-16: (7*8)+(6*7)+(5*3)+(4*0)+(3*8)+(2*1)+(1*6)=145 145 % 10 = 5 So 87308-16-5 is a valid CAS Registry Number.