The CAS Registry Mumber 24640-76-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,4,6,4 and 0 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 24640-76: (7*2)+(6*4)+(5*6)+(4*4)+(3*0)+(2*7)+(1*6)=104 104 % 10 = 4 So 24640-76-4 is a valid CAS Registry Number.