821921 has 8 divisors (see below), whose sum is σ = 873600. Its totient is φ = 771120.

The previous prime is 821911. The next prime is 821939. The reversal of 821921 is 129128.

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 821921 - 2⁶ = 821857 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (821911) 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, 3320 + ... + 3558.

It is an arithmetic number, because the mean of its divisors is an integer number (109200).

2⁸²¹⁹²¹ is an apocalyptic number.

It is an amenable number.

821921 is a deficient number, since it is larger than the sum of its proper divisors (51679).

821921 is a wasteful number, since it uses less digits than its factorization.

821921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 439.

The product of its digits is 288, while the sum is 23.

The square root of 821921 is about 906.5985881304. The cubic root of 821921 is about 93.6720501684.

The spelling of 821921 in words is "eight hundred twenty-one thousand, nine hundred twenty-one".