821001 has 8 divisors (see below), whose sum is σ = 1100704. Its totient is φ = 544320.

The previous prime is 820997. The next prime is 821003. The reversal of 821001 is 100128.

It is a happy number.

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

It is not a de Polignac number, because 821001 - 2² = 820997 is a prime.

It is a Duffinian number.

821001 is a lucky number.

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, 16 + ... + 1281.

It is an arithmetic number, because the mean of its divisors is an integer number (137588).

2⁸²¹⁰⁰¹ is an apocalyptic number.

It is an amenable number.

821001 is a deficient number, since it is larger than the sum of its proper divisors (279703).

821001 is a wasteful number, since it uses less digits than its factorization.

821001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1511.

The product of its (nonzero) digits is 16, while the sum is 12.

The square root of 821001 is about 906.0910550270. The cubic root of 821001 is about 93.6370871731.

Adding to 821001 its reverse (100128), we get a palindrome (921129).

The spelling of 821001 in words is "eight hundred twenty-one thousand, one".