681685 has 4 divisors (see below), whose sum is σ = 818028. Its totient is φ = 545344.

The previous prime is 681677. The next prime is 681689. The reversal of 681685 is 586186.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 586186 = 2 ⋅293093.

It can be written as a sum of positive squares in 2 ways, for example, as 194481 + 487204 = 441^2 + 698^2 .

It is a cyclic number.

It is not a de Polignac number, because 681685 - 2³ = 681677 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 681685.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681689) 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, 68164 + ... + 68173.

It is an arithmetic number, because the mean of its divisors is an integer number (204507).

2⁶⁸¹⁶⁸⁵ is an apocalyptic number.

It is an amenable number.

681685 is a deficient number, since it is larger than the sum of its proper divisors (136343).

681685 is a wasteful number, since it uses less digits than its factorization.

681685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136342.

The product of its digits is 11520, while the sum is 34.

The square root of 681685 is about 825.6421743104. The cubic root of 681685 is about 88.0091674334.

The spelling of 681685 in words is "six hundred eighty-one thousand, six hundred eighty-five".