Number of the day: 81813

Properties of the number 81813:

81813 = 3 × 27271 is semiprime and squarefree.
81813 has 2 distinct prime factors, 4 divisors, 33 antidivisors and 54540 totatives.
81813 has a semiprime digit sum 21 in base 10.
81813 has a Fibonacci digit sum 21 in base 10.
81813 has a triangular digit sum 21 in base 10.
Reversing the decimal digits of 81813 results in a sphenic number.
81813 = 40907² - 40906² = 13637² - 13634² is the difference of 2 nonnegative squares in 2 ways.
81813 is the sum of 2 positive triangular numbers.
81813 is the difference of 2 positive pentagonal numbers in 1 way.
81813 is the difference of 2 positive pentagonal pyramidal numbers in 1 way.
81813 = 1² + 4² + 286² is the sum of 3 positive squares.
81813² is the sum of 3 positive squares.
81813 is a proper divisor of 1901⁵⁴ - 1.
81813 is an emirpimes in (at least) the following bases: 3, 6, 7, 9, 15, 19, 33, 35, 48, 51, 55, 61, 67, 71, 78, 81, 85, and 99.
81813 is palindromic in (at least) base -55.
81813 in base 54 = S33 and consists of only the digits '3' and 'S'.

The number 81813 belongs to the following On-Line Encyclopedia of Integer Sequences (OEIS) sequences (among others):

Sequence numbers and descriptions below are taken from OEIS.
A053948: Numbers n such that n^2 contains only digits {3,6,9}.
A137041: Numbers n such that n and the square of n use only the digits 1, 3, 6, 8 and 9.