The CAS Registry Mumber 77547-89-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,5,4 and 7 respectively; the second part has 2 digits, 8 and 9 respectively. Calculate Digit Verification of CAS Registry Number 77547-89: (7*7)+(6*7)+(5*5)+(4*4)+(3*7)+(2*8)+(1*9)=178 178 % 10 = 8 So 77547-89-8 is a valid CAS Registry Number.