The CAS Registry Mumber 56473-23-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,6,4,7 and 3 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 56473-23: (7*5)+(6*6)+(5*4)+(4*7)+(3*3)+(2*2)+(1*3)=135 135 % 10 = 5 So 56473-23-5 is a valid CAS Registry Number.