Adding to 21455 its reverse (55412), we get a palindrome (76867).
It is a sphenic number, since it is the product of 3 distinct primes.
It is a cyclic number.
It is an Ulam number.
It is a Duffinian number.
It is a nialpdrome in base 15.
It is a congruent number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21455.
It is an unprimeable number.
221455 is an apocalyptic number.
21455 is an equidigital number, since it uses as much as digits as its factorization.
21455 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 625.
The square root of 21455 is about 146.4752538827. The cubic root of 21455 is about 27.7870754061.
The spelling of 21455 in words is "twenty-one thousand, four hundred fifty-five".