685561 has 8 divisors (see below), whose sum is σ = 733824. Its totient is φ = 638880.

The previous prime is 685547. The next prime is 685591. The reversal of 685561 is 165586.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 685561 - 2¹¹ = 683513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (685511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 580 + ... + 1306.

It is an arithmetic number, because the mean of its divisors is an integer number (91728).

2⁶⁸⁵⁵⁶¹ is an apocalyptic number.

It is an amenable number.

685561 is a deficient number, since it is larger than the sum of its proper divisors (48263).

685561 is a wasteful number, since it uses less digits than its factorization.

685561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 791.

The product of its digits is 7200, while the sum is 31.

The square root of 685561 is about 827.9861109946. The cubic root of 685561 is about 88.1756563713.

It can be divided in two parts, 6855 and 61, that multiplied together give a triangular number (418155 = T₉₁₄).

The spelling of 685561 in words is "six hundred eighty-five thousand, five hundred sixty-one".