The CAS Registry Mumber 100705-13-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,0,7,0 and 5 respectively; the second part has 2 digits, 1 and 3 respectively. Calculate Digit Verification of CAS Registry Number 100705-13: (8*1)+(7*0)+(6*0)+(5*7)+(4*0)+(3*5)+(2*1)+(1*3)=63 63 % 10 = 3 So 100705-13-3 is a valid CAS Registry Number.