Which is the odd number out 18 32 48 90?

Answer 1

Which one do you want it to be:

• 18, because it is a product of 3 primes;
• 32, because it is a power of a prime;
• 48, because it has five prime factors but is not a power of a prime;
• 90, because is is divisible by 5.

Take your pick!