The CAS Registry Mumber 77080-27-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,0,8 and 0 respectively; the second part has 2 digits, 2 and 7 respectively. Calculate Digit Verification of CAS Registry Number 77080-27: (7*7)+(6*7)+(5*0)+(4*8)+(3*0)+(2*2)+(1*7)=134 134 % 10 = 4 So 77080-27-4 is a valid CAS Registry Number.