The CAS Registry Mumber 173300-85-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,7,3,3,0 and 0 respectively; the second part has 2 digits, 8 and 5 respectively. Calculate Digit Verification of CAS Registry Number 173300-85: (8*1)+(7*7)+(6*3)+(5*3)+(4*0)+(3*0)+(2*8)+(1*5)=111 111 % 10 = 1 So 173300-85-1 is a valid CAS Registry Number.