821091 has 4 divisors (see below), whose sum is σ = 1094792. Its totient is φ = 547392.

The previous prime is 821089. The next prime is 821099. The reversal of 821091 is 190128.

821091 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 is not a de Polignac number, because 821091 - 2¹ = 821089 is a prime.

It is a D-number.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a nialpdrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821099) 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, 136846 + ... + 136851.

It is an arithmetic number, because the mean of its divisors is an integer number (273698).

2⁸²¹⁰⁹¹ is an apocalyptic number.

821091 is a deficient number, since it is larger than the sum of its proper divisors (273701).

821091 is a wasteful number, since it uses less digits than its factorization.

821091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273700.

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 821091 is about 906.1407175489. The cubic root of 821091 is about 93.6405086184.

The spelling of 821091 in words is "eight hundred twenty-one thousand, ninety-one".