The CAS Registry Mumber 26300-51-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,6,3,0 and 0 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 26300-51: (7*2)+(6*6)+(5*3)+(4*0)+(3*0)+(2*5)+(1*1)=76 76 % 10 = 6 So 26300-51-6 is a valid CAS Registry Number.