The CAS Registry Mumber 74813-45-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,8,1 and 3 respectively; the second part has 2 digits, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 74813-45: (7*7)+(6*4)+(5*8)+(4*1)+(3*3)+(2*4)+(1*5)=139 139 % 10 = 9 So 74813-45-9 is a valid CAS Registry Number.