101809 has 4 divisors (see below), whose sum is σ = 103540. Its totient is φ = 100080.

The previous prime is 101807. The next prime is 101833. The reversal of 101809 is 908101.

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

It can be written as a sum of positive squares in 2 ways, for example, as 23409 + 78400 = 153^2 + 280^2 .

It is a cyclic number.

It is not a de Polignac number, because 101809 - 2¹ = 101807 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (101807) 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, 774 + ... + 895.

It is an arithmetic number, because the mean of its divisors is an integer number (25885).

2¹⁰¹⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

101809 is a deficient number, since it is larger than the sum of its proper divisors (1731).

101809 is an equidigital number, since it uses as much as digits as its factorization.

101809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1730.

The product of its (nonzero) digits is 72, while the sum is 19.

The square root of 101809 is about 319.0752262398. The cubic root of 101809 is about 46.6941051791.

The spelling of 101809 in words is "one hundred one thousand, eight hundred nine".