The CAS Registry Mumber 51723-73-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,1,7,2 and 3 respectively; the second part has 2 digits, 7 and 3 respectively. Calculate Digit Verification of CAS Registry Number 51723-73: (7*5)+(6*1)+(5*7)+(4*2)+(3*3)+(2*7)+(1*3)=110 110 % 10 = 0 So 51723-73-0 is a valid CAS Registry Number.