688668 has 12 divisors (see below), whose sum is σ = 1606920. Its totient is φ = 229552.

The previous prime is 688661. The next prime is 688669. The reversal of 688668 is 866886.

It is a tau number, because it is divible by the number of its divisors (12).

It is a super-2 number, since 2×688668² = 948527228448, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688661) by changing a digit.

688668 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28683 + ... + 28706.

It is an arithmetic number, because the mean of its divisors is an integer number (133910).

2⁶⁸⁸⁶⁶⁸ is an apocalyptic number.

It is an amenable number.

688668 is an abundant number, since it is smaller than the sum of its proper divisors (918252).

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

688668 is a wasteful number, since it uses less digits than its factorization.

688668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57396 (or 57394 counting only the distinct ones).

The product of its digits is 110592, while the sum is 42.

The square root of 688668 is about 829.8602291953. The cubic root of 688668 is about 88.3086612794.

The spelling of 688668 in words is "six hundred eighty-eight thousand, six hundred sixty-eight".