42509 has 2 divisors, whose sum is σ = 42510. Its totient is φ = 42508.

The previous prime is 42499. The next prime is 42533. The reversal of 42509 is 90524.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 42025 + 484 = 205^2 + 22^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-42509 is a prime.

It is a Chen prime.

It is equal to p₄₄₄₈ and since 42509 and 4448 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42569) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21254 + 21255.

It is an arithmetic number, because the mean of its divisors is an integer number (21255).

2⁴²⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

42509 is a deficient number, since it is larger than the sum of its proper divisors (1).

42509 is an equidigital number, since it uses as much as digits as its factorization.

42509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 42509 is about 206.1771083316. The cubic root of 42509 is about 34.9001234249.

The spelling of 42509 in words is "forty-two thousand, five hundred nine".