42809 has 8 divisors (see below), whose sum is σ = 47880. Its totient is φ = 38016.

The previous prime is 42797. The next prime is 42821. The reversal of 42809 is 90824.

It is an interprime number because it is at equal distance from previous prime (42797) and next prime (42821).

It can be written as a sum of positive squares in 4 ways, for example, as 2809 + 40000 = 53^2 + 200^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 42809 - 2⁴ = 42793 is a prime.

It is a super-2 number, since 2×42809² = 3665220962, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (42829) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 437 + ... + 525.

It is an arithmetic number, because the mean of its divisors is an integer number (5985).

2⁴²⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

42809 is a deficient number, since it is larger than the sum of its proper divisors (5071).

42809 is a wasteful number, since it uses less digits than its factorization.

42809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 42809 is about 206.9033590834. The cubic root of 42809 is about 34.9820315932.

It can be divided in two parts, 4 and 2809, that multiplied together give a square (11236 = 106²).

The spelling of 42809 in words is "forty-two thousand, eight hundred nine".