681640 has 16 divisors (see below), whose sum is σ = 1533780. Its totient is φ = 272640.

The previous prime is 681631. The next prime is 681647. The reversal of 681640 is 46186.

It can be written as a sum of positive squares in 2 ways, for example, as 662596 + 19044 = 814^2 + 138^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681647) by changing a digit.

681640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8481 + ... + 8560.

2⁶⁸¹⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

681640 is an abundant number, since it is smaller than the sum of its proper divisors (852140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

681640 is a wasteful number, since it uses less digits than its factorization.

681640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17052 (or 17048 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 681640 is about 825.6149223458. The cubic root of 681640 is about 88.0072308108.

The spelling of 681640 in words is "six hundred eighty-one thousand, six hundred forty".