Number of the day: 688

Properties of the number 688:

688 = 2⁴ × 43 is the 563^th composite number and is not squarefree.
688 has 2 distinct prime factors, 10 divisors, 15 antidivisors and 336 totatives.
688 has a semiprime digit sum 22 in base 10.
Reversing the decimal digits of 688 results in a semiprime.
688 = 173² - 171² = 88² - 84² = 47² - 39² is the difference of 2 nonnegative squares in 3 ways.
688 is the sum of 2 positive triangular numbers.
688 is the difference of 2 positive pentagonal numbers in 1 way.
688 = 12² + 12² + 20² is the sum of 3 positive squares.
688² is the sum of 3 positive squares.
688 is a divisor of 257² - 1.
688 is palindromic in (at least) the following bases: 7, 12, 42, 85, and -11.
688 in base 3 = 221111 and consists of only the digits '1' and '2'.
688 in base 7 = 2002 and consists of only the digits '0' and '2'.
688 in base 9 = 844 and consists of only the digits '4' and '8'.
688 consists of only the digits '6' and '8'.
688 in base 12 = 494 and consists of only the digits '4' and '9'.
688 in base 18 = 224 and consists of only the digits '2' and '4'.

The number 688 belongs to the following On-Line Encyclopedia of Integer Sequences (OEIS) sequences (among others):

Sequence numbers and descriptions below are taken from OEIS.
A001743: Every digit contains at least one loop (version 1).
A006313: Numbers n such that n^16 + 1 is prime.
A008484: Number of partitions of n into parts >= 4.
A008598: Multiples of 16.
A014614: Numbers that are products of 5 primes (or 5-almost primes, a generalization of semiprimes).
A026797: Number of partitions of n in which the least part is 4.
A035607: Table a(d,m) of number of points of L1 norm m in cubic lattice Z^d, read by antidiagonals (d>=1, m >= 0).
A049600: Array T read by diagonals; T(i,j)=number of paths from (0,0) to (i,j) consisting of nonvertical segments (x(k),y(k))-to-(x(k+1),y(k+1)) such that 0=x(1)<x(2)<...<x(n-1)<x(n)=i, 0=y(1)<=y(2)<=...y(n-1)<=y(n)=j, for i >= 0, j >= 0.
A121028: Multiples of 8 containing a 8 in their decimal representation.
A178739: Product of the 4th power of a prime (A030514) and a different prime.