The CAS Registry Mumber 24399-54-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,4,3,9 and 9 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 24399-54: (7*2)+(6*4)+(5*3)+(4*9)+(3*9)+(2*5)+(1*4)=130 130 % 10 = 0 So 24399-54-0 is a valid CAS Registry Number.