688691 has 4 divisors (see below), whose sum is σ = 703392. Its totient is φ = 673992.

The previous prime is 688679. The next prime is 688697. The reversal of 688691 is 196886.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 196886 = 2 ⋅98443.

It is a cyclic number.

It is not a de Polignac number, because 688691 - 2⁶ = 688627 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 688691.

It is not an unprimeable number, because it can be changed into a prime (688697) 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, 7280 + ... + 7373.

It is an arithmetic number, because the mean of its divisors is an integer number (175848).

2⁶⁸⁸⁶⁹¹ is an apocalyptic number.

688691 is a deficient number, since it is larger than the sum of its proper divisors (14701).

688691 is a wasteful number, since it uses less digits than its factorization.

688691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14700.

The product of its digits is 20736, while the sum is 38.

The square root of 688691 is about 829.8740868349. The cubic root of 688691 is about 88.3096443736.

It can be divided in two parts, 6886 and 91, that multiplied together give a palindrome (626626).

The spelling of 688691 in words is "six hundred eighty-eight thousand, six hundred ninety-one".