The CAS Registry Mumber 103839-57-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,3,8,3 and 9 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 103839-57: (8*1)+(7*0)+(6*3)+(5*8)+(4*3)+(3*9)+(2*5)+(1*7)=122 122 % 10 = 2 So 103839-57-2 is a valid CAS Registry Number.