688639 has 4 divisors (see below), whose sum is σ = 787024. Its totient is φ = 590256.

The previous prime is 688637. The next prime is 688657. The reversal of 688639 is 936886.

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 688639 - 2¹ = 688637 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688631) 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, 49182 + ... + 49195.

It is an arithmetic number, because the mean of its divisors is an integer number (196756).

2⁶⁸⁸⁶³⁹ is an apocalyptic number.

688639 is a deficient number, since it is larger than the sum of its proper divisors (98385).

688639 is an equidigital number, since it uses as much as digits as its factorization.

688639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98384.

The product of its digits is 62208, while the sum is 40.

The square root of 688639 is about 829.8427561894. The cubic root of 688639 is about 88.3074216946.

The spelling of 688639 in words is "six hundred eighty-eight thousand, six hundred thirty-nine".