The CAS Registry Mumber 55975-64-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,5,9,7 and 5 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 55975-64: (7*5)+(6*5)+(5*9)+(4*7)+(3*5)+(2*6)+(1*4)=169 169 % 10 = 9 So 55975-64-9 is a valid CAS Registry Number.