161805 has 32 divisors (see below), whose sum is σ = 313344. Its totient is φ = 69696.

The previous prime is 161783. The next prime is 161807. The reversal of 161805 is 508161.

It is not a de Polignac number, because 161805 - 2⁵ = 161773 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161807) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2382 + ... + 2448.

It is an arithmetic number, because the mean of its divisors is an integer number (9792).

2¹⁶¹⁸⁰⁵ is an apocalyptic number.

161805 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

161805 is a deficient number, since it is larger than the sum of its proper divisors (151539).

161805 is a wasteful number, since it uses less digits than its factorization.

161805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105.

The product of its (nonzero) digits is 240, while the sum is 21.

The square root of 161805 is about 402.2499223120. The cubic root of 161805 is about 54.4917362551.

Adding to 161805 its reverse (508161), we get a palindrome (669966).

The spelling of 161805 in words is "one hundred sixty-one thousand, eight hundred five".