The CAS Registry Mumber 5842-73-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,8,4 and 2 respectively; the second part has 2 digits, 7 and 3 respectively. Calculate Digit Verification of CAS Registry Number 5842-73: (6*5)+(5*8)+(4*4)+(3*2)+(2*7)+(1*3)=109 109 % 10 = 9 So 5842-73-9 is a valid CAS Registry Number.