Search a number
-
+
21055 = 54211
BaseRepresentation
bin101001000111111
31001212211
411020333
51133210
6241251
7115246
oct51077
931784
1021055
1114901
1210227
139778
14795d
15638a
hex523f

21055 has 4 divisors (see below), whose sum is σ = 25272. Its totient is φ = 16840.

The previous prime is 21031. The next prime is 21059. The reversal of 21055 is 55012.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21055 - 25 = 21023 is a prime.

It is a Smith number, since the sum of its digits (13) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

21055 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21059) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2101 + ... + 2110.

It is an arithmetic number, because the mean of its divisors is an integer number (6318).

221055 is an apocalyptic number.

21055 is a deficient number, since it is larger than the sum of its proper divisors (4217).

21055 is an equidigital number, since it uses as much as digits as its factorization.

21055 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4216.

The product of its (nonzero) digits is 50, while the sum is 13.

The square root of 21055 is about 145.1034114003. The cubic root of 21055 is about 27.6133066130.

Adding to 21055 its reverse (55012), we get a palindrome (76067).

The spelling of 21055 in words is "twenty-one thousand, fifty-five".

Divisors: 1 5 4211 21055