The CAS Registry Mumber 1117777-07-7 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,1,1,7,7,7 and 7 respectively; the second part has 2 digits, 0 and 7 respectively. Calculate Digit Verification of CAS Registry Number 1117777-07: (9*1)+(8*1)+(7*1)+(6*7)+(5*7)+(4*7)+(3*7)+(2*0)+(1*7)=157 157 % 10 = 7 So 1117777-07-7 is a valid CAS Registry Number.