Prime numbers / Rust exercise (updated)

// Rust exercise
// Find prime numbers

fn is_prime(number: u64) -> bool {
    // Returns true if given number is a prime
    if number == 2 || number == 3 {
        return true
    }
    if number <= 1 || number % 2 == 0 || number % 3 == 0 {
        return false
    }
    let max_number = (number as f64).sqrt() as u64 + 1;

    for i in (5..max_number).step_by(2) {
        if number % i == 0 {
            return false
        }
    }
    return true
}

fn check_primes(to_number: u64) -> Vec<u64> {
    // Checks is there any primes between 0 and given value (to_number)
    // and pushes all prime numbers to vector as a result
    let mut multiplier = 1;
    let mut potential_prime = 6*multiplier;
    let mut primes = Vec::new();

    if to_number >= 2 {
        primes.push(2);
    }
    if to_number >= 3 {
        primes.push(3);
    }

    while potential_prime<to_number {
        if is_prime(potential_prime-1) {
            primes.push(potential_prime-1);
        }
        if is_prime(potential_prime+1) {
            primes.push(potential_prime+1);
        }
        multiplier += 1;
        potential_prime = 6*multiplier;
    }
    return primes;
}

fn main() {
    let primes = check_primes(1000000);
    println!("{:?}", primes[primes.len()-1]) ;
}