684821 has 4 divisors (see below), whose sum is σ = 706944. Its totient is φ = 662700.

The previous prime is 684809. The next prime is 684829. The reversal of 684821 is 128486.

684821 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, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 684821 - 2⁶ = 684757 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (684829) 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, 11015 + ... + 11076.

It is an arithmetic number, because the mean of its divisors is an integer number (176736).

2⁶⁸⁴⁸²¹ is an apocalyptic number.

It is an amenable number.

684821 is a deficient number, since it is larger than the sum of its proper divisors (22123).

684821 is a wasteful number, since it uses less digits than its factorization.

684821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22122.

The product of its digits is 3072, while the sum is 29.

The square root of 684821 is about 827.5391229422. The cubic root of 684821 is about 88.1439191143.

The spelling of 684821 in words is "six hundred eighty-four thousand, eight hundred twenty-one".