Professor Cardy

Prime Number Calculator

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


79813 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: `79813` is 1 more than `79812` (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 `79813` is `6370114969`. Subtracting 1, we get `6370114968`. Note that `6370114968 ÷ 24 = 265421457`.

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: `79813 = 39907^2 - 39906^2 = 1592568649 - 1592488836`

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: `79813 = 17^2 + 282^2 = 289 + 79524`, where `79813 = 4 × 19953 + 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: `79813` is of the form `4n+1`, where `n = 19953`.

The First 10,000 Prime Numbers