Number of the day: 21928

Properties of the number 21928:

21928 = 2³ × 2741 is the 19470^th composite number and is not squarefree.
21928 has 2 distinct prime factors, 8 divisors, 21 antidivisors and 10960 totatives.
21928 has a semiprime digit sum 22 in base 10.
21928 = 5483² - 5481² = 2743² - 2739² is the difference of 2 nonnegative squares in 2 ways.
21928 is the difference of 2 positive pentagonal numbers in 2 ways.
21928 = 42² + 142² is the sum of 2 positive squares in 1 way.
21928 = 78² + 88² + 90² is the sum of 3 positive squares.
21928² = 11928² + 18400² is the sum of 2 positive squares in 1 way.
21928² is the sum of 3 positive squares.
21928 is a proper divisor of 449²⁰ - 1.
21928 is palindromic in (at least) the following bases: -35, and -84.
21928 in base 28 = rr4 and consists of only the digits '4' and 'r'.
21928 in base 34 = iww and consists of only the digits 'i' and 'w'.

The number 21928 belongs to the following On-Line Encyclopedia of Integer Sequences (OEIS) sequences (among others):

Sequence numbers and descriptions below are taken from OEIS.
A002257: Numbers n such that 13*4^n + 1 is prime.
A036063: Increasing gaps among twin primes: size.
A075454: Integer averages of two successive perfect powers (pp(n) + pp(n+1))/2.
A093928: a(n) = sum( A073698(k), k=1...n )^(1/n).
A198016: Number of isomorphism classes of nanocones with 4 pentagons and a nearsymmetric boundary of length n
A233075: Numbers that are midway between the nearest square and the nearest cube.
A235893: T(n,k)=Number of (n+1)X(k+1) 0..3 arrays with the minimum plus the upper median equal to the lower median plus the maximum in every 2X2 subblock
A238869: Number of partitions of n where the difference between consecutive parts is at most 9.
A252201: T(n,k)=Number of (n+2)X(k+2) 0..3 arrays with every 3X3 subblock row, column, diagonal and antidiagonal sum not equal to 0 3 5 6 or 7
A261228: a(n) = number of steps to reach 0 when starting from k = (n^3)-1 and repeatedly applying the map that replaces k with k - A055401(k), where A055401(k) = the number of positive cubes needed to sum to k using the greedy algorithm.