The CAS Registry Mumber 72730-68-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,2,7,3 and 0 respectively; the second part has 2 digits, 6 and 8 respectively. Calculate Digit Verification of CAS Registry Number 72730-68: (7*7)+(6*2)+(5*7)+(4*3)+(3*0)+(2*6)+(1*8)=128 128 % 10 = 8 So 72730-68-8 is a valid CAS Registry Number.