The CAS Registry Mumber 23251-65-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,3,2,5 and 1 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 23251-65: (7*2)+(6*3)+(5*2)+(4*5)+(3*1)+(2*6)+(1*5)=82 82 % 10 = 2 So 23251-65-2 is a valid CAS Registry Number.