209823 has 4 divisors (see below), whose sum is σ = 279768. Its totient is φ = 139880.

The previous prime is 209821. The next prime is 209837. The reversal of 209823 is 328902.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 209823 - 2¹ = 209821 is a prime.

It is a D-number.

It is a plaindrome in base 16.

It is a zygodrome in base 2.

It is a junction number, because it is equal to n+sod(n) for n = 209793 and 209802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209821) 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, 34968 + ... + 34973.

It is an arithmetic number, because the mean of its divisors is an integer number (69942).

2²⁰⁹⁸²³ is an apocalyptic number.

209823 is a deficient number, since it is larger than the sum of its proper divisors (69945).

209823 is an equidigital number, since it uses as much as digits as its factorization.

209823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69944.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 209823 is about 458.0644059518. The cubic root of 209823 is about 59.4225152434.

The spelling of 209823 in words is "two hundred nine thousand, eight hundred twenty-three".