The CAS Registry Mumber 76544-01-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,5,4 and 4 respectively; the second part has 2 digits, 0 and 1 respectively. Calculate Digit Verification of CAS Registry Number 76544-01: (7*7)+(6*6)+(5*5)+(4*4)+(3*4)+(2*0)+(1*1)=139 139 % 10 = 9 So 76544-01-9 is a valid CAS Registry Number.