The CAS Registry Mumber 2881-87-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,8,8 and 1 respectively; the second part has 2 digits, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 2881-87: (6*2)+(5*8)+(4*8)+(3*1)+(2*8)+(1*7)=110 110 % 10 = 0 So 2881-87-0 is a valid CAS Registry Number.