# isprime(::BigInt, ?)

isprime(x::BigInt, [reps = 25]) -> Bool

Probabilistic primality test. Returns `true` if `x` is prime; and `false` if `x` is not prime with high probability. The false positive rate is about `0.25^reps`. `reps = 25` is considered safe for cryptographic applications (Knuth, Seminumerical Algorithms).

``````julia> isprime(big(3))
true``````

## Examples

The `isprime(::Integer)` function in Julia determines whether a given integer `x` is prime or not. It returns `true` if `x` is prime and `false` otherwise.

``````julia> isprime(3)
true``````

Here are some common examples of using the `isprime` function:

1. Check if a number is prime:

``````julia> isprime(7)
true``````
2. Verify if a large number is prime:

``````julia> isprime(10^9 + 7)
true``````
3. Identify non-prime numbers:

``````julia> isprime(10)
false``````
4. Use the function in a conditional statement:
``````julia> num = 13;
julia> if isprime(num)
println("\$num is prime")
else
println("\$num is not prime")
end``````

Please note that the `isprime` function works only with integers. If a non-integer value is passed, an error will occur.