681805 has 4 divisors (see below), whose sum is σ = 818172. Its totient is φ = 545440.

The previous prime is 681787. The next prime is 681809. The reversal of 681805 is 508186.

It is a happy number.

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 454276 + 227529 = 674^2 + 477^2 .

It is not a de Polignac number, because 681805 - 2⁵ = 681773 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 (681809) 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, 68176 + ... + 68185.

It is an arithmetic number, because the mean of its divisors is an integer number (204543).

2⁶⁸¹⁸⁰⁵ is an apocalyptic number.

It is an amenable number.

681805 is a deficient number, since it is larger than the sum of its proper divisors (136367).

681805 is a wasteful number, since it uses less digits than its factorization.

681805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136366.

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 681805 is about 825.7148418189. The cubic root of 681805 is about 88.0143313436.

The spelling of 681805 in words is "six hundred eighty-one thousand, eight hundred five".