The CAS Registry Mumber 103930-26-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,3,9,3 and 0 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 103930-26: (8*1)+(7*0)+(6*3)+(5*9)+(4*3)+(3*0)+(2*2)+(1*6)=93 93 % 10 = 3 So 103930-26-3 is a valid CAS Registry Number.