The CAS Registry Mumber 104825-42-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,4,8,2 and 5 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 104825-42: (8*1)+(7*0)+(6*4)+(5*8)+(4*2)+(3*5)+(2*4)+(1*2)=105 105 % 10 = 5 So 104825-42-5 is a valid CAS Registry Number.