The CAS Registry Mumber 1727-64-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,7,2 and 7 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 1727-64: (6*1)+(5*7)+(4*2)+(3*7)+(2*6)+(1*4)=86 86 % 10 = 6 So 1727-64-6 is a valid CAS Registry Number.