The CAS Registry Mumber 56739-96-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,6,7,3 and 9 respectively; the second part has 2 digits, 9 and 6 respectively. Calculate Digit Verification of CAS Registry Number 56739-96: (7*5)+(6*6)+(5*7)+(4*3)+(3*9)+(2*9)+(1*6)=169 169 % 10 = 9 So 56739-96-9 is a valid CAS Registry Number.