684640 has 48 divisors (see below), whose sum is σ = 1769040. Its totient is φ = 248320.

The previous prime is 684637. The next prime is 684643. The reversal of 684640 is 46486.

It is an interprime number because it is at equal distance from previous prime (684637) and next prime (684643).

It is a junction number, because it is equal to n+sod(n) for n = 684599 and 684608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (684643) 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, 1566 + ... + 1954.

It is an arithmetic number, because the mean of its divisors is an integer number (36855).

2⁶⁸⁴⁶⁴⁰ 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 684640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (884520).

684640 is an abundant number, since it is smaller than the sum of its proper divisors (1084400).

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

684640 is a wasteful number, since it uses less digits than its factorization.

684640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 415 (or 407 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 28.

The square root of 684640 is about 827.4297553267. The cubic root of 684640 is about 88.1361528731.

It can be divided in two parts, 6846 and 40, that added together give a palindrome (6886).

The spelling of 684640 in words is "six hundred eighty-four thousand, six hundred forty".