The CAS Registry Mumber 18077-34-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,0,7 and 7 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 18077-34: (7*1)+(6*8)+(5*0)+(4*7)+(3*7)+(2*3)+(1*4)=114 114 % 10 = 4 So 18077-34-4 is a valid CAS Registry Number.