The CAS Registry Mumber 142733-51-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,4,2,7,3 and 3 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 142733-51: (8*1)+(7*4)+(6*2)+(5*7)+(4*3)+(3*3)+(2*5)+(1*1)=115 115 % 10 = 5 So 142733-51-5 is a valid CAS Registry Number.