The CAS Registry Mumber 77573-68-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,5,7 and 3 respectively; the second part has 2 digits, 6 and 8 respectively. Calculate Digit Verification of CAS Registry Number 77573-68: (7*7)+(6*7)+(5*5)+(4*7)+(3*3)+(2*6)+(1*8)=173 173 % 10 = 3 So 77573-68-3 is a valid CAS Registry Number.