The CAS Registry Mumber 511-72-8 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 5,1 and 1 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 511-72: (5*5)+(4*1)+(3*1)+(2*7)+(1*2)=48 48 % 10 = 8 So 511-72-8 is a valid CAS Registry Number.