209109823 has 4 divisors (see below), whose sum is σ = 225195208. Its totient is φ = 193024440.

The previous prime is 209109821. The next prime is 209109827. The reversal of 209109823 is 328901902.

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 209109823 - 2¹ = 209109821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209109821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8042673 + ... + 8042698.

It is an arithmetic number, because the mean of its divisors is an integer number (56298802).

Almost surely, 2^209109823 is an apocalyptic number.

209109823 is a deficient number, since it is larger than the sum of its proper divisors (16085385).

209109823 is a wasteful number, since it uses less digits than its factorization.

209109823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16085384.

The product of its (nonzero) digits is 7776, while the sum is 34.

The square root of 209109823 is about 14460.6301038371. The cubic root of 209109823 is about 593.5511418567.

The spelling of 209109823 in words is "two hundred nine million, one hundred nine thousand, eight hundred twenty-three".