680821 has 4 divisors (see below), whose sum is σ = 692044. Its totient is φ = 669600.

The previous prime is 680809. The next prime is 680831. The reversal of 680821 is 128086.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 18225 + 662596 = 135^2 + 814^2 .

It is a cyclic number.

It is not a de Polignac number, because 680821 - 2¹¹ = 678773 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 (680831) 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 3 ways as a sum of consecutive naturals, for example, 5520 + ... + 5641.

It is an arithmetic number, because the mean of its divisors is an integer number (173011).

2⁶⁸⁰⁸²¹ is an apocalyptic number.

680821 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

680821 is a deficient number, since it is larger than the sum of its proper divisors (11223).

680821 is a wasteful number, since it uses less digits than its factorization.

680821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11222.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 680821 is about 825.1187793282. The cubic root of 680821 is about 87.9719693781.

The spelling of 680821 in words is "six hundred eighty thousand, eight hundred twenty-one".