The CAS Registry Mumber 58013-42-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,8,0,1 and 3 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 58013-42: (7*5)+(6*8)+(5*0)+(4*1)+(3*3)+(2*4)+(1*2)=106 106 % 10 = 6 So 58013-42-6 is a valid CAS Registry Number.