The CAS Registry Mumber 51031-50-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,1,0,3 and 1 respectively; the second part has 2 digits, 5 and 0 respectively. Calculate Digit Verification of CAS Registry Number 51031-50: (7*5)+(6*1)+(5*0)+(4*3)+(3*1)+(2*5)+(1*0)=66 66 % 10 = 6 So 51031-50-6 is a valid CAS Registry Number.