161865 has 32 divisors (see below), whose sum is σ = 316800. Its totient is φ = 77760.

The previous prime is 161839. The next prime is 161869. The reversal of 161865 is 568161.

It is not a de Polignac number, because 161865 - 2¹⁰ = 160841 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161869) 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, 1431 + ... + 1539.

It is an arithmetic number, because the mean of its divisors is an integer number (9900).

2¹⁶¹⁸⁶⁵ is an apocalyptic number.

161865 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

161865 is a deficient number, since it is larger than the sum of its proper divisors (154935).

161865 is a wasteful number, since it uses less digits than its factorization.

161865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134 (or 128 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 161865 is about 402.3244958985. The cubic root of 161865 is about 54.4984709051.

161865 divided by its sum of digits (27) gives a palindrome (5995).

It can be divided in two parts, 16 and 1865, that added together give a palindrome (1881).

The spelling of 161865 in words is "one hundred sixty-one thousand, eight hundred sixty-five".