The CAS Registry Mumber 107100-00-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,7,1,0 and 0 respectively; the second part has 2 digits, 0 and 0 respectively. Calculate Digit Verification of CAS Registry Number 107100-00: (8*1)+(7*0)+(6*7)+(5*1)+(4*0)+(3*0)+(2*0)+(1*0)=55 55 % 10 = 5 So 107100-00-5 is a valid CAS Registry Number.