The CAS Registry Mumber 27473-55-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,7,4,7 and 3 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 27473-55: (7*2)+(6*7)+(5*4)+(4*7)+(3*3)+(2*5)+(1*5)=128 128 % 10 = 8 So 27473-55-8 is a valid CAS Registry Number.