The CAS Registry Mumber 75841-71-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,8,4 and 1 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 75841-71: (7*7)+(6*5)+(5*8)+(4*4)+(3*1)+(2*7)+(1*1)=153 153 % 10 = 3 So 75841-71-3 is a valid CAS Registry Number.