The CAS Registry Mumber 1542-49-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,5,4 and 2 respectively; the second part has 2 digits, 4 and 9 respectively. Calculate Digit Verification of CAS Registry Number 1542-49: (6*1)+(5*5)+(4*4)+(3*2)+(2*4)+(1*9)=70 70 % 10 = 0 So 1542-49-0 is a valid CAS Registry Number.