The CAS Registry Mumber 81038-50-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,0,3 and 8 respectively; the second part has 2 digits, 5 and 0 respectively. Calculate Digit Verification of CAS Registry Number 81038-50: (7*8)+(6*1)+(5*0)+(4*3)+(3*8)+(2*5)+(1*0)=108 108 % 10 = 8 So 81038-50-8 is a valid CAS Registry Number.