The CAS Registry Mumber 37984-91-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,7,9,8 and 4 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 37984-91: (7*3)+(6*7)+(5*9)+(4*8)+(3*4)+(2*9)+(1*1)=171 171 % 10 = 1 So 37984-91-1 is a valid CAS Registry Number.