The CAS Registry Mumber 142720-78-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,4,2,7,2 and 0 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 142720-78: (8*1)+(7*4)+(6*2)+(5*7)+(4*2)+(3*0)+(2*7)+(1*8)=113 113 % 10 = 3 So 142720-78-3 is a valid CAS Registry Number.