The CAS Registry Mumber 49805-23-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,9,8,0 and 5 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 49805-23: (7*4)+(6*9)+(5*8)+(4*0)+(3*5)+(2*2)+(1*3)=144 144 % 10 = 4 So 49805-23-4 is a valid CAS Registry Number.