The CAS Registry Mumber 38731-86-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,8,7,3 and 1 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 38731-86: (7*3)+(6*8)+(5*7)+(4*3)+(3*1)+(2*8)+(1*6)=141 141 % 10 = 1 So 38731-86-1 is a valid CAS Registry Number.