165521 has 4 divisors (see below), whose sum is σ = 167232. Its totient is φ = 163812.

The previous prime is 165511. The next prime is 165523. The reversal of 165521 is 125561.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 125561 = 241 ⋅521.

It is a cyclic number.

It is not a de Polignac number, because 165521 - 2⁶ = 165457 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 14.

It is a junction number, because it is equal to n+sod(n) for n = 165493 and 165502.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 165521.

It is not an unprimeable number, because it can be changed into a prime (165523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 701 + ... + 906.

It is an arithmetic number, because the mean of its divisors is an integer number (41808).

2¹⁶⁵⁵²¹ is an apocalyptic number.

It is an amenable number.

165521 is a deficient number, since it is larger than the sum of its proper divisors (1711).

165521 is a wasteful number, since it uses less digits than its factorization.

165521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1710.

The product of its digits is 300, while the sum is 20.

The square root of 165521 is about 406.8427214539. The cubic root of 165521 is about 54.9057338435.

It can be divided in two parts, 165 and 521, that added together give a palindrome (686).

The spelling of 165521 in words is "one hundred sixty-five thousand, five hundred twenty-one".