The CAS Registry Mumber 75875-71-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,8,7 and 5 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 75875-71: (7*7)+(6*5)+(5*8)+(4*7)+(3*5)+(2*7)+(1*1)=177 177 % 10 = 7 So 75875-71-7 is a valid CAS Registry Number.