# 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

## See Also

digits, inf, isdigit, iseven, isfinite, isless, islower, isnumber, isodd, isprime, isqrt, issorted, issubnormal, isxdigit, nan,## User Contributed Notes

### Add a Note

The format of note supported is markdown, use triple backtick to start and end a code block.