2509 has 4 divisors (see below), whose sum is σ = 2716.
Its totient is φ = 2304.
The previous prime is 2503. The next prime is 2521. The reversal of 2509 is 9052.
2509 is nontrivially palindromic in base 12.
It is a semiprime because it is the product of two primes.
It can be written as a sum of positive squares in 2 ways, for example, as 484 + 2025 = 22^2 + 45^2
It is a 4-Lehmer number, since φ(2509) divides (2509-1)4.
It is a cyclic number.
It is not a de Polignac number, because 2509 - 25 = 2477 is a prime.
It is an alternating number because its digits alternate between even and odd.
It is a Duffinian number.
It is a plaindrome in base 16.
It is a nialpdrome in base 14.
It is a junction number, because it is equal to n+sod(n) for n = 2492 and 2501.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (2503) 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 in 3 ways as a sum of consecutive naturals, for example, 84 + ... + 109.
It is an arithmetic number, because the mean of its divisors is an integer number (679).
2509 is a Friedman number, since it can be written as 50^2+9, using all its digits and the basic arithmetic operations.
It is an amenable number.
2509 is a deficient number, since it is larger than the sum of its proper divisors (207).
2509 is a wasteful number, since it uses less digits than its factorization.
2509 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 206.
The product of its (nonzero) digits is 90, while the sum is 16.
The square root of 2509 is about 50.0899191455.
The cubic root of 2509 is about 13.5883550839.
The spelling of 2509 in words is "two thousand, five hundred nine".