The CAS Registry Mumber 1125-72-0 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 5 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 1125-72: (6*1)+(5*1)+(4*2)+(3*5)+(2*7)+(1*2)=50 50 % 10 = 0 So 1125-72-0 is a valid CAS Registry Number.