The CAS Registry Mumber 291506-89-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,9,1,5,0 and 6 respectively; the second part has 2 digits, 8 and 9 respectively. Calculate Digit Verification of CAS Registry Number 291506-89: (8*2)+(7*9)+(6*1)+(5*5)+(4*0)+(3*6)+(2*8)+(1*9)=153 153 % 10 = 3 So 291506-89-3 is a valid CAS Registry Number.