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21361 = 41521
BaseRepresentation
bin101001101110001
31002022011
411031301
51140421
6242521
7116164
oct51561
932264
1021361
111505a
1210441
139952
147adb
1564e1
hex5371

21361 has 4 divisors (see below), whose sum is σ = 21924. Its totient is φ = 20800.

The previous prime is 21347. The next prime is 21377. The reversal of 21361 is 16312.

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

It can be written as a sum of positive squares in 2 ways, for example, as 3136 + 18225 = 56^2 + 135^2 .

It is a cyclic number.

It is not a de Polignac number, because 21361 - 29 = 20849 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.

It is a nialpdrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21341) 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, 220 + ... + 301.

It is an arithmetic number, because the mean of its divisors is an integer number (5481).

221361 is an apocalyptic number.

It is an amenable number.

21361 is a deficient number, since it is larger than the sum of its proper divisors (563).

21361 is an equidigital number, since it uses as much as digits as its factorization.

21361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 562.

The product of its digits is 36, while the sum is 13.

The square root of 21361 is about 146.1540283400. The cubic root of 21361 is about 27.7464351669.

Adding to 21361 its reverse (16312), we get a palindrome (37673).

The spelling of 21361 in words is "twenty-one thousand, three hundred sixty-one".

Divisors: 1 41 521 21361