The CAS Registry Mumber 103665-49-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,3,6,6 and 5 respectively; the second part has 2 digits, 4 and 9 respectively. Calculate Digit Verification of CAS Registry Number 103665-49: (8*1)+(7*0)+(6*3)+(5*6)+(4*6)+(3*5)+(2*4)+(1*9)=112 112 % 10 = 2 So 103665-49-2 is a valid CAS Registry Number.