The CAS Registry Mumber 27051-10-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,7,0,5 and 1 respectively; the second part has 2 digits, 1 and 0 respectively. Calculate Digit Verification of CAS Registry Number 27051-10: (7*2)+(6*7)+(5*0)+(4*5)+(3*1)+(2*1)+(1*0)=81 81 % 10 = 1 So 27051-10-1 is a valid CAS Registry Number.