821491 has 16 divisors (see below), whose sum is σ = 995328. Its totient is φ = 668800.

The previous prime is 821489. The next prime is 821497. The reversal of 821491 is 194128.

It is a happy number.

821491 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 821491 - 2¹ = 821489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821497) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4206 + ... + 4396.

It is an arithmetic number, because the mean of its divisors is an integer number (62208).

2⁸²¹⁴⁹¹ is an apocalyptic number.

821491 is a deficient number, since it is larger than the sum of its proper divisors (173837).

821491 is a wasteful number, since it uses less digits than its factorization.

821491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 242.

The product of its digits is 576, while the sum is 25.

The square root of 821491 is about 906.3614069454. The cubic root of 821491 is about 93.6557120176.

The spelling of 821491 in words is "eight hundred twenty-one thousand, four hundred ninety-one".