399909569 has 4 divisors (see below), whose sum is σ = 400077444. Its totient is φ = 399741696.

The previous prime is 399909541. The next prime is 399909659. The reversal of 399909569 is 965909993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 965909993 = 24551 ⋅39343.

It can be written as a sum of positive squares in 2 ways, for example, as 179238544 + 220671025 = 13388^2 + 14855^2 .

It is a cyclic number.

It is not a de Polignac number, because 399909569 - 2⁸ = 399909313 is a prime.

It is a super-2 number, since 2×399909569² = 319855326755531522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (399909509) 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, 80312 + ... + 85145.

It is an arithmetic number, because the mean of its divisors is an integer number (100019361).

Almost surely, 2^399909569 is an apocalyptic number.

It is an amenable number.

399909569 is a deficient number, since it is larger than the sum of its proper divisors (167875).

399909569 is a wasteful number, since it uses less digits than its factorization.

399909569 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167874.

The product of its (nonzero) digits is 5314410, while the sum is 59.

The square root of 399909569 is about 19997.7390972080. The cubic root of 399909569 is about 736.7507704345.

The spelling of 399909569 in words is "three hundred ninety-nine million, nine hundred nine thousand, five hundred sixty-nine".