Summation of the First Two Million Primes with Rust

Project Euler problem number 10 - Summation of primes - is stated as follows. The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million.

#![feature(iterator_step_by)]

fn is_prime(n: u64) -> bool {
    if n == 2 || n == 3 {
        return true;
    } else if (n < 2) || (n % 2 == 0) {
        return false;
    }
    let upper_limit = (n as f64).sqrt() as u64;
    (3..upper_limit + 1)
        .step_by(2)
        .find(|i| n % i == 0)
        .is_none()
}

fn sum_primes_below(n: u64) -> u64 {
    (0..n).filter(|x| is_prime(*x)).sum()
}

fn main() {
    let n = 2_000_000;
    let sum = sum_primes_below(n);
    println!("The Sum of the first {} primes is {}.", n, sum);
}