209855 has 12 divisors (see below), whose sum is σ = 270840. Its totient is φ = 155664.

The previous prime is 209851. The next prime is 209857. The reversal of 209855 is 558902.

209855 = 55² + 56² + ... + 92².

It is not a de Polignac number, because 209855 - 2² = 209851 is a prime.

It is a plaindrome in base 14 and base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4442 + ... + 4488.

It is an arithmetic number, because the mean of its divisors is an integer number (22570).

2²⁰⁹⁸⁵⁵ is an apocalyptic number.

209855 is a deficient number, since it is larger than the sum of its proper divisors (60985).

209855 is an equidigital number, since it uses as much as digits as its factorization.

209855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118 (or 71 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 29.

The square root of 209855 is about 458.0993342060. The cubic root of 209855 is about 59.4255359225.

The spelling of 209855 in words is "two hundred nine thousand, eight hundred fifty-five".