The CAS Registry Mumber 2478-50-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,4,7 and 8 respectively; the second part has 2 digits, 5 and 0 respectively. Calculate Digit Verification of CAS Registry Number 2478-50: (6*2)+(5*4)+(4*7)+(3*8)+(2*5)+(1*0)=94 94 % 10 = 4 So 2478-50-4 is a valid CAS Registry Number.