687440 has 40 divisors (see below), whose sum is σ = 1723848. Its totient is φ = 253440.

The previous prime is 687437. The next prime is 687443. The reversal of 687440 is 44786.

687440 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (687437) and next prime (687443).

It can be written as a sum of positive squares in 4 ways, for example, as 53824 + 633616 = 232^2 + 796^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (687443) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 710 + ... + 1370.

2⁶⁸⁷⁴⁴⁰ 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 687440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (861924).

687440 is an abundant number, since it is smaller than the sum of its proper divisors (1036408).

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

687440 is a wasteful number, since it uses less digits than its factorization.

687440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 687 (or 681 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 29.

The square root of 687440 is about 829.1200154381. The cubic root of 687440 is about 88.2561407824.

The spelling of 687440 in words is "six hundred eighty-seven thousand, four hundred forty".