The CAS Registry Mumber 28863-50-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,8,8,6 and 3 respectively; the second part has 2 digits, 5 and 0 respectively. Calculate Digit Verification of CAS Registry Number 28863-50: (7*2)+(6*8)+(5*8)+(4*6)+(3*3)+(2*5)+(1*0)=145 145 % 10 = 5 So 28863-50-5 is a valid CAS Registry Number.