678821 has 16 divisors (see below), whose sum is σ = 822528. Its totient is φ = 552000.

The previous prime is 678809. The next prime is 678823. The reversal of 678821 is 128876.

It is a cyclic number.

It is not a de Polignac number, because 678821 - 2⁶ = 678757 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 (678823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6671 + ... + 6771.

It is an arithmetic number, because the mean of its divisors is an integer number (51408).

2⁶⁷⁸⁸²¹ is an apocalyptic number.

It is an amenable number.

678821 is a deficient number, since it is larger than the sum of its proper divisors (143707).

678821 is a wasteful number, since it uses less digits than its factorization.

678821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172.

The product of its digits is 5376, while the sum is 32.

The square root of 678821 is about 823.9059412336. The cubic root of 678821 is about 87.8857418643.

Subtracting from 678821 its reverse (128876), we obtain a palindrome (549945).

It can be divided in two parts, 67 and 8821, that added together give a palindrome (8888).

The spelling of 678821 in words is "six hundred seventy-eight thousand, eight hundred twenty-one".