681690 has 32 divisors (see below), whose sum is σ = 1691136. Its totient is φ = 175680.

The previous prime is 681689. The next prime is 681719. The reversal of 681690 is 96186.

It is a super-2 number, since 2×681690² = 929402512200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a Curzon number.

It is an unprimeable 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 15 ways as a sum of consecutive naturals, for example, 564 + ... + 1296.

It is an arithmetic number, because the mean of its divisors is an integer number (52848).

2⁶⁸¹⁶⁹⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 681690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (845568).

681690 is an abundant number, since it is smaller than the sum of its proper divisors (1009446).

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

681690 is a wasteful number, since it uses less digits than its factorization.

681690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 774.

The product of its (nonzero) digits is 2592, while the sum is 30.

The square root of 681690 is about 825.6452022509. The cubic root of 681690 is about 88.0093826084.

The spelling of 681690 in words is "six hundred eighty-one thousand, six hundred ninety".