The CAS Registry Mumber 16739-75-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,6,7,3 and 9 respectively; the second part has 2 digits, 7 and 5 respectively. Calculate Digit Verification of CAS Registry Number 16739-75: (7*1)+(6*6)+(5*7)+(4*3)+(3*9)+(2*7)+(1*5)=136 136 % 10 = 6 So 16739-75-6 is a valid CAS Registry Number.