The CAS Registry Mumber 74757-97-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,7,5 and 7 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 74757-97: (7*7)+(6*4)+(5*7)+(4*5)+(3*7)+(2*9)+(1*7)=174 174 % 10 = 4 So 74757-97-4 is a valid CAS Registry Number.