The CAS Registry Mumber 28976-53-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,8,9,7 and 6 respectively; the second part has 2 digits, 5 and 3 respectively. Calculate Digit Verification of CAS Registry Number 28976-53: (7*2)+(6*8)+(5*9)+(4*7)+(3*6)+(2*5)+(1*3)=166 166 % 10 = 6 So 28976-53-6 is a valid CAS Registry Number.