The CAS Registry Mumber 74775-97-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,7,7 and 5 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 74775-97: (7*7)+(6*4)+(5*7)+(4*7)+(3*5)+(2*9)+(1*7)=176 176 % 10 = 6 So 74775-97-6 is a valid CAS Registry Number.