4, 9, 25 and 49
They are squares of prime numbers.
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All prime numbers less than 50 have exactly two factors.
e.g. 2,3,5,7,11,13,17,19,23,29,31,37,41,43 & 47.
All numbers that have exactly two factors are prime numbers whereas composite numbers have more than two factors.
Prime squares have three factors. There are 11 of them in that range.
11,22,33,44,55,66,77,88,99
If the GCF of a given pair of numbers is 1, the LCM will be equal to their product. If the GCF is greater than 1, the LCM will be less than their product. Or, stated another way, if the two numbers have no common prime factors, their LCM will be their product.
There are 10 numbers less than 101 which have an odd number of factors: 1,4,9,16,25,36,49,64,81,100.