688651 has 4 divisors (see below), whose sum is σ = 697032. Its totient is φ = 680272.

The previous prime is 688637. The next prime is 688657. The reversal of 688651 is 156886.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 688651 - 2⁹ = 688139 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (688657) by changing a digit.

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, 4066 + ... + 4231.

It is an arithmetic number, because the mean of its divisors is an integer number (174258).

2⁶⁸⁸⁶⁵¹ is an apocalyptic number.

688651 is a deficient number, since it is larger than the sum of its proper divisors (8381).

688651 is an equidigital number, since it uses as much as digits as its factorization.

688651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8380.

The product of its digits is 11520, while the sum is 34.

The square root of 688651 is about 829.8499864433. The cubic root of 688651 is about 88.3079346304.

The spelling of 688651 in words is "six hundred eighty-eight thousand, six hundred fifty-one".