The CAS Registry Mumber 1090-01-3 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,0,9 and 0 respectively; the second part has 2 digits, 0 and 1 respectively. Calculate Digit Verification of CAS Registry Number 1090-01: (6*1)+(5*0)+(4*9)+(3*0)+(2*0)+(1*1)=43 43 % 10 = 3 So 1090-01-3 is a valid CAS Registry Number.