The CAS Registry Mumber 1240278-21-0 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,2,4,0,2,7 and 8 respectively; the second part has 2 digits, 2 and 1 respectively. Calculate Digit Verification of CAS Registry Number 1240278-21: (9*1)+(8*2)+(7*4)+(6*0)+(5*2)+(4*7)+(3*8)+(2*2)+(1*1)=120 120 % 10 = 0 So 1240278-21-0 is a valid CAS Registry Number.