The CAS Registry Mumber 164073-77-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,6,4,0,7 and 3 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 164073-77: (8*1)+(7*6)+(6*4)+(5*0)+(4*7)+(3*3)+(2*7)+(1*7)=132 132 % 10 = 2 So 164073-77-2 is a valid CAS Registry Number.