The CAS Registry Mumber 107165-63-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,7,1,6 and 5 respectively; the second part has 2 digits, 6 and 3 respectively. Calculate Digit Verification of CAS Registry Number 107165-63: (8*1)+(7*0)+(6*7)+(5*1)+(4*6)+(3*5)+(2*6)+(1*3)=109 109 % 10 = 9 So 107165-63-9 is a valid CAS Registry Number.