394218309 has 4 divisors (see below), whose sum is σ = 525624416. Its totient is φ = 262812204.

The previous prime is 394218299. The next prime is 394218343. The reversal of 394218309 is 903812493.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 903812493 = 3 ⋅301270831.

It is not a de Polignac number, because 394218309 - 2⁸ = 394218053 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (394218359) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65703049 + ... + 65703054.

It is an arithmetic number, because the mean of its divisors is an integer number (131406104).

Almost surely, 2^394218309 is an apocalyptic number.

It is an amenable number.

394218309 is a deficient number, since it is larger than the sum of its proper divisors (131406107).

394218309 is a wasteful number, since it uses less digits than its factorization.

394218309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131406106.

The product of its (nonzero) digits is 46656, while the sum is 39.

The square root of 394218309 is about 19854.9316040121. The cubic root of 394218309 is about 733.2390683012.

The spelling of 394218309 in words is "three hundred ninety-four million, two hundred eighteen thousand, three hundred nine".