The CAS Registry Mumber 123380-74-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,3,3,8 and 0 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 123380-74: (8*1)+(7*2)+(6*3)+(5*3)+(4*8)+(3*0)+(2*7)+(1*4)=105 105 % 10 = 5 So 123380-74-5 is a valid CAS Registry Number.