The CAS Registry Mumber 4019-90-3 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,0,1 and 9 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 4019-90: (6*4)+(5*0)+(4*1)+(3*9)+(2*9)+(1*0)=73 73 % 10 = 3 So 4019-90-3 is a valid CAS Registry Number.