209540 has 12 divisors (see below), whose sum is σ = 440076. Its totient is φ = 83808.

The previous prime is 209533. The next prime is 209543. The reversal of 209540 is 45902.

It can be written as a sum of positive squares in 2 ways, for example, as 118336 + 91204 = 344^2 + 302^2 .

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 10477 = 209540 / (2 + 0 + 9 + 5 + 4 + 0).

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 209540.

It is not an unprimeable number, because it can be changed into a prime (209543) 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, 5219 + ... + 5258.

It is an arithmetic number, because the mean of its divisors is an integer number (36673).

2²⁰⁹⁵⁴⁰ is an apocalyptic number.

209540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

209540 is an abundant number, since it is smaller than the sum of its proper divisors (230536).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

209540 is a wasteful number, since it uses less digits than its factorization.

209540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10486 (or 10484 counting only the distinct ones).

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

The square root of 209540 is about 457.7553931960. The cubic root of 209540 is about 59.3957877350.

The spelling of 209540 in words is "two hundred nine thousand, five hundred forty".