181021 has 4 divisors (see below), whose sum is σ = 182332. Its totient is φ = 179712.

The previous prime is 181019. The next prime is 181031. The reversal of 181021 is 120181.

181021 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.

It can be written as a sum of positive squares in 2 ways, for example, as 99225 + 81796 = 315^2 + 286^2 .

It is a cyclic number.

It is not a de Polignac number, because 181021 - 2¹ = 181019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 180992 and 181010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181001) 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, 420 + ... + 733.

It is an arithmetic number, because the mean of its divisors is an integer number (45583).

2¹⁸¹⁰²¹ is an apocalyptic number.

It is an amenable number.

181021 is a deficient number, since it is larger than the sum of its proper divisors (1311).

181021 is a wasteful number, since it uses less digits than its factorization.

181021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1310.

The product of its (nonzero) digits is 16, while the sum is 13.

The square root of 181021 is about 425.4656272838. The cubic root of 181021 is about 56.5687158294.

The spelling of 181021 in words is "one hundred eighty-one thousand, twenty-one".