The CAS Registry Mumber 596-86-1 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 5,9 and 6 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 596-86: (5*5)+(4*9)+(3*6)+(2*8)+(1*6)=101 101 % 10 = 1 So 596-86-1 is a valid CAS Registry Number.