The CAS Registry Mumber 15839-65-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,5,8,3 and 9 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 15839-65: (7*1)+(6*5)+(5*8)+(4*3)+(3*9)+(2*6)+(1*5)=133 133 % 10 = 3 So 15839-65-3 is a valid CAS Registry Number.