The CAS Registry Mumber 80078-61-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,0,7 and 8 respectively; the second part has 2 digits, 6 and 1 respectively. Calculate Digit Verification of CAS Registry Number 80078-61: (7*8)+(6*0)+(5*0)+(4*7)+(3*8)+(2*6)+(1*1)=121 121 % 10 = 1 So 80078-61-1 is a valid CAS Registry Number.