Rust Min Perimeter Rectangle
fn min_perimeter_rectangle(n: i64) -> i64 {
    let mut i = 1i64;
    let mut min = i64::MAX;
    while i * i < n {
        if n % i == 0 {
            min = min.min(2 * (i + n / i));
        }
        i += 1;
    }

    min
}

This searches factor pairs up to the square root and picks the pair with the smallest perimeter.