111809 has 4 divisors (see below), whose sum is σ = 118404. Its totient is φ = 105216.

The previous prime is 111799. The next prime is 111821. The reversal of 111809 is 908111.

111809 = 40² + 41² + ... + 73².

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 908111 = 601 ⋅1511.

It can be written as a sum of positive squares in 2 ways, for example, as 102400 + 9409 = 320^2 + 97^2 .

It is a cyclic number.

It is not a de Polignac number, because 111809 - 2¹² = 107713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (111829) 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, 3272 + ... + 3305.

It is an arithmetic number, because the mean of its divisors is an integer number (29601).

2¹¹¹⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

111809 is a deficient number, since it is larger than the sum of its proper divisors (6595).

111809 is an equidigital number, since it uses as much as digits as its factorization.

111809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6594.

The product of its (nonzero) digits is 72, while the sum is 20.

The square root of 111809 is about 334.3785280188. The cubic root of 111809 is about 48.1754286704.

The spelling of 111809 in words is "one hundred eleven thousand, eight hundred nine".