The CAS Registry Mumber 76053-71-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,0,5 and 3 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 76053-71: (7*7)+(6*6)+(5*0)+(4*5)+(3*3)+(2*7)+(1*1)=129 129 % 10 = 9 So 76053-71-9 is a valid CAS Registry Number.