How many odd factors does 210 have?  Pick:
A) 3 B) 4 C) 5 D) 6 E) 8
Start with the prime factorization: 210 = 2*3*5*7   For odd factors, we put aside the factor of two, and look at the other prime factors.   set of exponents = {1, 1, 1}   plus 1 to each = {2, 2, 2}   product = 2*2*2= 
<gadget id="calculator">2*2*2</gadget>
<output>8</output>
8   Therefore, there are 8 odd factors of 210. In case you are curious, they are {1, 3, 5, 7, 15, 21, 35, and 105}   Answer: 8.
<result>E</result>
How many odd factors does 210 have?