123509 has 4 divisors (see below), whose sum is σ = 124716. Its totient is φ = 122304.

The previous prime is 123503. The next prime is 123517. The reversal of 123509 is 905321.

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 62500 + 61009 = 250^2 + 247^2 .

It is a cyclic number.

It is not a de Polignac number, because 123509 - 2⁴ = 123493 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (123503) 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, 434 + ... + 659.

It is an arithmetic number, because the mean of its divisors is an integer number (31179).

2¹²³⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

123509 is a deficient number, since it is larger than the sum of its proper divisors (1207).

123509 is a wasteful number, since it uses less digits than its factorization.

123509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1206.

The product of its (nonzero) digits is 270, while the sum is 20.

The square root of 123509 is about 351.4384725667. The cubic root of 123509 is about 49.8004042913.

The spelling of 123509 in words is "one hundred twenty-three thousand, five hundred nine".