The CAS Registry Mumber 74794-55-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,7,9 and 4 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 74794-55: (7*7)+(6*4)+(5*7)+(4*9)+(3*4)+(2*5)+(1*5)=171 171 % 10 = 1 So 74794-55-1 is a valid CAS Registry Number.