Professor Cardy

Prime Number Calculator

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Enter an integer (max. 1,000,000)


40241 is a prime number.

About the Calculator

This calculator performs the decomposition of a number into its prime factors and lists all its natural divisors. Enter an integer between 1 and 1,000,000.

Curiosities

1) Relation to multiples of 6: Every prime number greater than 3 is always one less or one more than a multiple of 6.
Example: `40241` is 1 less than `40242` (multiple of 6).

2) Square minus 1 divisible by 24: For every prime number greater than 3, if 1 is subtracted from its square, the result is always divisible by 24.
Example: The square of `40241` is `1619338081`. Subtracting 1, we get `1619338080`. Note that `1619338080 ÷ 24 = 67472420`.

3) Difference of squares: Every prime number greater than 2 can be expressed as the difference of the squares of two consecutive natural numbers.
Example: `40241 = 20121^2 - 20120^2 = 404854641 - 404814400`

4) Sum of two squares: Every prime number of the form `4n+1` (where n is a positive natural number) can be expressed as the sum of two squares.
Example: `40241 = 121^2 + 160^2 = 14641 + 25600`, where `40241 = 4 × 10060 + 1`.

5) Form `4n+1` or `4n-1`: Except for the number 2, all prime numbers follow the pattern `4n+1` or `4n-1`, where `n` is a natural number.
Example: `40241` is of the form `4n+1`, where `n = 10060`.

The First 10,000 Prime Numbers