The CAS Registry Mumber 20940-00-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,0,9,4 and 0 respectively; the second part has 2 digits, 0 and 0 respectively. Calculate Digit Verification of CAS Registry Number 20940-00: (7*2)+(6*0)+(5*9)+(4*4)+(3*0)+(2*0)+(1*0)=75 75 % 10 = 5 So 20940-00-5 is a valid CAS Registry Number.