409

This number is a prime.

"FORMULA 409" claims that it "cleans and degreases virtually any hard, nonporous surface; no rinsing required."

A high-powered Chevrolet engine introduced in 1961 measured 409 cubic inches, which was large for its time. It was immortalized by the Beach Boys in the song "409" which starts out, "She's real fine, my 409." [Litman]

The concatenation of the first 409 odd numbers in reverse order is prime. [Gupta]

The smallest prime which along with both its neighbors uses non-prime digits (401, 409, 419). [Murthy]

The product of the positive even digits plus the sum of the odd digits. [Silva]

There are 409 distinct twin primes below ten thousand. [Beedassy]

Largest prime number that is smaller than the square of its smallest primitive root. [Dunkelblau]

The smallest prime number that has a digital root of 4. All other digital roots are represented by smaller primes except for 6 and 9 which cannot be digital roots of primes. [Gaydos]

Smallest prime whose smallest positive primitive root is odd and composite. [Vantieghem]

The smallest prime number that becomes a pandigital prime number (2561387420489) when each of its digits d is replaced by d^d. [Gaydos]

The smallest holey Cyclops prime. [Gupta]

The smallest Cyclops prime that does not become a smaller prime when its zero is removed. [Gaydos]

The highest point in Washington DC is 409 feet above sea level. [Gaydos]

409 and the 409th palindrome (31013) are both Cyclops primes. [Gaydos]