The CAS Registry Mumber 5588-71-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,5,8 and 8 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 5588-71: (6*5)+(5*5)+(4*8)+(3*8)+(2*7)+(1*1)=126 126 % 10 = 6 So 5588-71-6 is a valid CAS Registry Number.