The CAS Registry Mumber 90508-26-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,0,5,0 and 8 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 90508-26: (7*9)+(6*0)+(5*5)+(4*0)+(3*8)+(2*2)+(1*6)=122 122 % 10 = 2 So 90508-26-2 is a valid CAS Registry Number.