The CAS Registry Mumber 287923-10-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,8,7,9,2 and 3 respectively; the second part has 2 digits, 1 and 0 respectively. Calculate Digit Verification of CAS Registry Number 287923-10: (8*2)+(7*8)+(6*7)+(5*9)+(4*2)+(3*3)+(2*1)+(1*0)=178 178 % 10 = 8 So 287923-10-8 is a valid CAS Registry Number.