688521 has 4 divisors (see below), whose sum is σ = 918032. Its totient is φ = 459012.

The previous prime is 688511. The next prime is 688531. The reversal of 688521 is 125886.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (688511) and next prime (688531).

It is not a de Polignac number, because 688521 - 2⁷ = 688393 is a prime.

It is a super-2 number, since 2×688521² = 948122334882, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 688521.

It is not an unprimeable number, because it can be changed into a prime (688511) 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, 114751 + ... + 114756.

It is an arithmetic number, because the mean of its divisors is an integer number (229508).

2⁶⁸⁸⁵²¹ is an apocalyptic number.

It is an amenable number.

688521 is a deficient number, since it is larger than the sum of its proper divisors (229511).

688521 is a wasteful number, since it uses less digits than its factorization.

688521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229510.

The product of its digits is 3840, while the sum is 30.

The square root of 688521 is about 829.7716553366. The cubic root of 688521 is about 88.3023775079.

Adding to 688521 its sum of digits (30), we get a triangular number (688551 = T₁₁₇₃).

The spelling of 688521 in words is "six hundred eighty-eight thousand, five hundred twenty-one".