Prime numbers

Note these numbers are not prime numbers

87.............divisible by 3
111-----divisible by 3
117, divisible by 13, 9, 3
119 divisible by 17, 7

remember the telephone no. 4422322321 for prime numbers in 2 digit.
what does it mean,
between 0 -10 ----------4 prime nos.
between 10-20----------4 prime nos.
between 20-30----------2 prime nos.
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between 90-100---------1 prime no.

There are total of 25 prime numbers between 0 - 100

note 1 is not a prime number.

2 is the only even prime number.

37 is the only prime number, whose individual digits are prime, and when the digits are reversed, ie. 73, it is still a prime number.

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