The CAS Registry Mumber 55385-72-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,5,3,8 and 5 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 55385-72: (7*5)+(6*5)+(5*3)+(4*8)+(3*5)+(2*7)+(1*2)=143 143 % 10 = 3 So 55385-72-3 is a valid CAS Registry Number.