The CAS Registry Mumber 2487-77-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,4,8 and 7 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 2487-77: (6*2)+(5*4)+(4*8)+(3*7)+(2*7)+(1*7)=106 106 % 10 = 6 So 2487-77-6 is a valid CAS Registry Number.