21455 has 8 divisors (see below), whose sum is σ = 29472. Its totient is φ = 14688.
The previous prime is 21433. The next prime is 21467. The reversal of 21455 is 55412.
It is a sphenic number, since it is the product of 3 distinct primes.
It is a cyclic number.
It is not a de Polignac number, because 21455 - 26 = 21391 is a prime.
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.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 272 + ... + 341.
It is an arithmetic number, because the mean of its divisors is an integer number (3684).
It is the magic constant of a 35 × 35 magic square.
221455 is an apocalyptic number.
21455 is a deficient number, since it is larger than the sum of its proper divisors (8017).
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 product of its digits is 200, while the sum is 17.
The square root of 21455 is about 146.4752538827. The cubic root of 21455 is about 27.7870754061.
Adding to 21455 its reverse (55412), we get a palindrome (76867).
The spelling of 21455 in words is "twenty-one thousand, four hundred fifty-five".
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