The CAS Registry Mumber 153304-68-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,3,3,0 and 4 respectively; the second part has 2 digits, 6 and 8 respectively. Calculate Digit Verification of CAS Registry Number 153304-68: (8*1)+(7*5)+(6*3)+(5*3)+(4*0)+(3*4)+(2*6)+(1*8)=108 108 % 10 = 8 So 153304-68-8 is a valid CAS Registry Number.