The CAS Registry Mumber 107321-97-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,7,3,2 and 1 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 107321-97: (8*1)+(7*0)+(6*7)+(5*3)+(4*2)+(3*1)+(2*9)+(1*7)=101 101 % 10 = 1 So 107321-97-1 is a valid CAS Registry Number.