161321 has 4 divisors (see below), whose sum is σ = 162132. Its totient is φ = 160512.

The previous prime is 161309. The next prime is 161323. The reversal of 161321 is 123161.

161321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 123161 = 79 ⋅1559.

It can be written as a sum of positive squares in 2 ways, for example, as 105625 + 55696 = 325^2 + 236^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161321 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 161296 and 161305.

It is not an unprimeable number, because it can be changed into a prime (161323) 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, 125 + ... + 581.

It is an arithmetic number, because the mean of its divisors is an integer number (40533).

2¹⁶¹³²¹ is an apocalyptic number.

It is an amenable number.

161321 is a deficient number, since it is larger than the sum of its proper divisors (811).

161321 is an equidigital number, since it uses as much as digits as its factorization.

161321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 810.

The product of its digits is 36, while the sum is 14.

The square root of 161321 is about 401.6478557144. The cubic root of 161321 is about 54.4373490993.

Adding to 161321 its reverse (123161), we get a palindrome (284482).

It can be divided in two parts, 161 and 321, that multiplied together give a triangular number (51681 = T₃₂₁).

The spelling of 161321 in words is "one hundred sixty-one thousand, three hundred twenty-one".