The CAS Registry Mumber 124435-18-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,4,4,3 and 5 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 124435-18: (8*1)+(7*2)+(6*4)+(5*4)+(4*3)+(3*5)+(2*1)+(1*8)=103 103 % 10 = 3 So 124435-18-3 is a valid CAS Registry Number.