The CAS Registry Mumber 1151668-24-4 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,1,5,1,6,6 and 8 respectively; the second part has 2 digits, 2 and 4 respectively. Calculate Digit Verification of CAS Registry Number 1151668-24: (9*1)+(8*1)+(7*5)+(6*1)+(5*6)+(4*6)+(3*8)+(2*2)+(1*4)=144 144 % 10 = 4 So 1151668-24-4 is a valid CAS Registry Number.