The CAS Registry Mumber 75473-21-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,4,7 and 3 respectively; the second part has 2 digits, 2 and 1 respectively. Calculate Digit Verification of CAS Registry Number 75473-21: (7*7)+(6*5)+(5*4)+(4*7)+(3*3)+(2*2)+(1*1)=141 141 % 10 = 1 So 75473-21-1 is a valid CAS Registry Number.