16021 has 4 divisors (see below), whose sum is σ = 16492. Its totient is φ = 15552.

The previous prime is 16007. The next prime is 16033. The reversal of 16021 is 12061.

16021 = 89² + 90².

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12061 = 7 ⋅1723.

It can be written as a sum of positive squares in 2 ways, for example, as 8100 + 7921 = 90^2 + 89^2 .

It is a 3-Lehmer number, since φ(16021) divides (16021-1)³.

It is a cyclic number.

It is not a de Polignac number, because 16021 - 2¹³ = 7829 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 4 and base 12.

It is a zygodrome in base 4.

It is a junction number, because it is equal to n+sod(n) for n = 15989 and 16007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16001) 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, 180 + ... + 253.

It is an arithmetic number, because the mean of its divisors is an integer number (4123).

2¹⁶⁰²¹ is an apocalyptic number.

16021 is the 90-th centered square number.

It is an amenable number.

16021 is a deficient number, since it is larger than the sum of its proper divisors (471).

16021 is an equidigital number, since it uses as much as digits as its factorization.

16021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 470.

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 16021 is about 126.5740889756. The cubic root of 16021 is about 25.2094404875.

Adding to 16021 its reverse (12061), we get a palindrome (28082).

It can be divided in two parts, 160 and 21, that added together give a palindrome (181).

The spelling of 16021 in words is "sixteen thousand, twenty-one".