The CAS Registry Mumber 107741-26-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,7,7,4 and 1 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 107741-26: (8*1)+(7*0)+(6*7)+(5*7)+(4*4)+(3*1)+(2*2)+(1*6)=114 114 % 10 = 4 So 107741-26-4 is a valid CAS Registry Number.