681985 has 4 divisors (see below), whose sum is σ = 818388. Its totient is φ = 545584.

The previous prime is 681983. The next prime is 681997. The reversal of 681985 is 589186.

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 150544 + 531441 = 388^2 + 729^2 .

It is a cyclic number.

It is not a de Polignac number, because 681985 - 2¹ = 681983 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (681983) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68194 + ... + 68203.

It is an arithmetic number, because the mean of its divisors is an integer number (204597).

It is a Proth number, since it is equal to 333 ⋅ 2¹¹ + 1 and 333 < 2¹¹.

2⁶⁸¹⁹⁸⁵ is an apocalyptic number.

It is an amenable number.

681985 is a deficient number, since it is larger than the sum of its proper divisors (136403).

681985 is a wasteful number, since it uses less digits than its factorization.

681985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136402.

The product of its digits is 17280, while the sum is 37.

The square root of 681985 is about 825.8238310923. The cubic root of 681985 is about 88.0220760730.

The spelling of 681985 in words is "six hundred eighty-one thousand, nine hundred eighty-five".