821009 has 8 divisors (see below), whose sum is σ = 987840. Its totient is φ = 666576.

The previous prime is 821003. The next prime is 821027. The reversal of 821009 is 900128.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 821009 - 2⁸ = 820753 is a prime.

It is a plaindrome in base 15.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (821003) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2954 + ... + 3219.

It is an arithmetic number, because the mean of its divisors is an integer number (123480).

2⁸²¹⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

821009 is a deficient number, since it is larger than the sum of its proper divisors (166831).

821009 is a wasteful number, since it uses less digits than its factorization.

821009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6199.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 821009 is about 906.0954695836. The cubic root of 821009 is about 93.6373913117.

The spelling of 821009 in words is "eight hundred twenty-one thousand, nine".