681940 has 24 divisors (see below), whose sum is σ = 1636992. Its totient is φ = 233760.

The previous prime is 681931. The next prime is 681943. The reversal of 681940 is 49186.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 681899 and 681908.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681943) by changing a digit.

681940 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 7 ways as a sum of consecutive naturals, for example, 2296 + ... + 2575.

It is an arithmetic number, because the mean of its divisors is an integer number (68208).

2⁶⁸¹⁹⁴⁰ is an apocalyptic number.

It is an amenable number.

681940 is an abundant number, since it is smaller than the sum of its proper divisors (955052).

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

681940 is a wasteful number, since it uses less digits than its factorization.

681940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4887 (or 4885 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 681940 is about 825.7965851225. The cubic root of 681940 is about 88.0201400184.

It can be divided in two parts, 6819 and 40, that added together give a cube (6859 = 19³).

The spelling of 681940 in words is "six hundred eighty-one thousand, nine hundred forty".