The CAS Registry Mumber 445-71-6 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 4,4 and 5 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 445-71: (5*4)+(4*4)+(3*5)+(2*7)+(1*1)=66 66 % 10 = 6 So 445-71-6 is a valid CAS Registry Number.