The CAS Registry Mumber 41945-55-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,1,9,4 and 5 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 41945-55: (7*4)+(6*1)+(5*9)+(4*4)+(3*5)+(2*5)+(1*5)=125 125 % 10 = 5 So 41945-55-5 is a valid CAS Registry Number.