The CAS Registry Mumber 89724-38-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,9,7,2 and 4 respectively; the second part has 2 digits, 3 and 8 respectively. Calculate Digit Verification of CAS Registry Number 89724-38: (7*8)+(6*9)+(5*7)+(4*2)+(3*4)+(2*3)+(1*8)=179 179 % 10 = 9 So 89724-38-9 is a valid CAS Registry Number.