The CAS Registry Mumber 1124-45-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,1,2 and 4 respectively; the second part has 2 digits, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 1124-45: (6*1)+(5*1)+(4*2)+(3*4)+(2*4)+(1*5)=44 44 % 10 = 4 So 1124-45-4 is a valid CAS Registry Number.