The CAS Registry Mumber 124663-65-6 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, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 124663-65: (8*1)+(7*2)+(6*4)+(5*6)+(4*6)+(3*3)+(2*6)+(1*5)=126 126 % 10 = 6 So 124663-65-6 is a valid CAS Registry Number.