The CAS Registry Mumber 89920-24-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,9,9,2 and 0 respectively; the second part has 2 digits, 2 and 4 respectively. Calculate Digit Verification of CAS Registry Number 89920-24: (7*8)+(6*9)+(5*9)+(4*2)+(3*0)+(2*2)+(1*4)=171 171 % 10 = 1 So 89920-24-1 is a valid CAS Registry Number.