The CAS Registry Mumber 51110-41-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,1,1,1 and 0 respectively; the second part has 2 digits, 4 and 1 respectively. Calculate Digit Verification of CAS Registry Number 51110-41: (7*5)+(6*1)+(5*1)+(4*1)+(3*0)+(2*4)+(1*1)=59 59 % 10 = 9 So 51110-41-9 is a valid CAS Registry Number.