688981 has 4 divisors (see below), whose sum is σ = 692172. Its totient is φ = 685792.

The previous prime is 688979. The next prime is 688999. The reversal of 688981 is 189886.

It is a happy number.

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 133956 + 555025 = 366^2 + 745^2 .

It is a cyclic number.

It is not a de Polignac number, because 688981 - 2¹ = 688979 is a prime.

It is a super-2 number, since 2×688981² = 949389636722, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688951) 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, 1246 + ... + 1711.

It is an arithmetic number, because the mean of its divisors is an integer number (173043).

2⁶⁸⁸⁹⁸¹ is an apocalyptic number.

It is an amenable number.

688981 is a deficient number, since it is larger than the sum of its proper divisors (3191).

688981 is a wasteful number, since it uses less digits than its factorization.

688981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3190.

The product of its digits is 27648, while the sum is 40.

The square root of 688981 is about 830.0487937465. The cubic root of 688981 is about 88.3220380320.

It can be divided in two parts, 6889 and 81, that multiplied together give a square (558009 = 747²).

The spelling of 688981 in words is "six hundred eighty-eight thousand, nine hundred eighty-one".