688649 has 4 divisors (see below), whose sum is σ = 741636. Its totient is φ = 635664.

The previous prime is 688637. The next prime is 688657. The reversal of 688649 is 946886.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 946886 = 2 ⋅473443.

It can be written as a sum of positive squares in 2 ways, for example, as 366025 + 322624 = 605^2 + 568^2 .

It is a cyclic number.

It is not a de Polignac number, because 688649 - 2⁸ = 688393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (688669) 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, 26474 + ... + 26499.

It is an arithmetic number, because the mean of its divisors is an integer number (185409).

2⁶⁸⁸⁶⁴⁹ is an apocalyptic number.

It is an amenable number.

688649 is a deficient number, since it is larger than the sum of its proper divisors (52987).

688649 is a wasteful number, since it uses less digits than its factorization.

688649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52986.

The product of its digits is 82944, while the sum is 41.

The square root of 688649 is about 829.8487814054. The cubic root of 688649 is about 88.3078491415.

The spelling of 688649 in words is "six hundred eighty-eight thousand, six hundred forty-nine".