Professor Cardy

Prime Number Calculator

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


85889 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: `85889` is 1 less than `85890` (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 `85889` is `7376920321`. Subtracting 1, we get `7376920320`. Note that `7376920320 ÷ 24 = 307371680`.

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: `85889 = 42945^2 - 42944^2 = 1844273025 - 1844187136`

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: `85889 = 25^2 + 292^2 = 625 + 85264`, where `85889 = 4 × 21472 + 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: `85889` is of the form `4n+1`, where `n = 21472`.

The First 10,000 Prime Numbers