The CAS Registry Mumber 124663-72-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,4,6,6 and 3 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 124663-72: (8*1)+(7*2)+(6*4)+(5*6)+(4*6)+(3*3)+(2*7)+(1*2)=125 125 % 10 = 5 So 124663-72-5 is a valid CAS Registry Number.