The CAS Registry Mumber 3860-91-1 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,8,6 and 0 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 3860-91: (6*3)+(5*8)+(4*6)+(3*0)+(2*9)+(1*1)=101 101 % 10 = 1 So 3860-91-1 is a valid CAS Registry Number.