The CAS Registry Mumber 124281-76-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,4,2,8 and 1 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 124281-76: (8*1)+(7*2)+(6*4)+(5*2)+(4*8)+(3*1)+(2*7)+(1*6)=111 111 % 10 = 1 So 124281-76-1 is a valid CAS Registry Number.