The CAS Registry Mumber 124126-12-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,4,1,2 and 6 respectively; the second part has 2 digits, 1 and 2 respectively. Calculate Digit Verification of CAS Registry Number 124126-12: (8*1)+(7*2)+(6*4)+(5*1)+(4*2)+(3*6)+(2*1)+(1*2)=81 81 % 10 = 1 So 124126-12-1 is a valid CAS Registry Number.