The CAS Registry Mumber 107027-78-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,7,0,2 and 7 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 107027-78: (8*1)+(7*0)+(6*7)+(5*0)+(4*2)+(3*7)+(2*7)+(1*8)=101 101 % 10 = 1 So 107027-78-1 is a valid CAS Registry Number.