The CAS Registry Mumber 20472-56-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,0,4,7 and 2 respectively; the second part has 2 digits, 5 and 6 respectively. Calculate Digit Verification of CAS Registry Number 20472-56: (7*2)+(6*0)+(5*4)+(4*7)+(3*2)+(2*5)+(1*6)=84 84 % 10 = 4 So 20472-56-4 is a valid CAS Registry Number.