The CAS Registry Mumber 173323-70-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,7,3,3,2 and 3 respectively; the second part has 2 digits, 7 and 0 respectively. Calculate Digit Verification of CAS Registry Number 173323-70: (8*1)+(7*7)+(6*3)+(5*3)+(4*2)+(3*3)+(2*7)+(1*0)=121 121 % 10 = 1 So 173323-70-1 is a valid CAS Registry Number.