The CAS Registry Mumber 74101-28-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,1,0 and 1 respectively; the second part has 2 digits, 2 and 8 respectively. Calculate Digit Verification of CAS Registry Number 74101-28: (7*7)+(6*4)+(5*1)+(4*0)+(3*1)+(2*2)+(1*8)=93 93 % 10 = 3 So 74101-28-3 is a valid CAS Registry Number.