The CAS Registry Mumber 1828-40-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,8,2 and 8 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 1828-40: (6*1)+(5*8)+(4*2)+(3*8)+(2*4)+(1*0)=86 86 % 10 = 6 So 1828-40-6 is a valid CAS Registry Number.