681688 has 48 divisors (see below), whose sum is σ = 1559520. Its totient is φ = 278208.

The previous prime is 681677. The next prime is 681689. The reversal of 681688 is 886186.

681688 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a zygodrome in base 6.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681689) by changing a digit.

681688 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 11 ways as a sum of consecutive naturals, for example, 14481 + ... + 14527.

It is an arithmetic number, because the mean of its divisors is an integer number (32490).

2⁶⁸¹⁶⁸⁸ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 681688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (779760).

681688 is an abundant number, since it is smaller than the sum of its proper divisors (877832).

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

681688 is a wasteful number, since it uses less digits than its factorization.

681688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104 (or 93 counting only the distinct ones).

The product of its digits is 18432, while the sum is 37.

The square root of 681688 is about 825.6439910761. The cubic root of 681688 is about 88.0092965385.

It can be divided in two parts, 681 and 688, that added together give a square (1369 = 37²).

The spelling of 681688 in words is "six hundred eighty-one thousand, six hundred eighty-eight".