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21405 = 351427
BaseRepresentation
bin101001110011101
31002100210
411032131
51141110
6243033
7116256
oct51635
932323
1021405
111509a
1210479
139987
147b2d
156520
hex539d

21405 has 8 divisors (see below), whose sum is σ = 34272. Its totient is φ = 11408.

The previous prime is 21401. The next prime is 21407. The reversal of 21405 is 50412.

21405 is nontrivially palindromic in base 9.

21405 is an esthetic number in base 9, because in such base its adjacent digits differ by 1.

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 21405 - 22 = 21401 is a prime.

21405 is an undulating number in base 9.

21405 is a lucky number.

It is a nialpdrome in base 13 and 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 21405.

It is not an unprimeable number, because it can be changed into a prime (21401) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 699 + ... + 728.

It is an arithmetic number, because the mean of its divisors is an integer number (4284).

221405 is an apocalyptic number.

It is an amenable number.

21405 is a deficient number, since it is larger than the sum of its proper divisors (12867).

21405 is a wasteful number, since it uses less digits than its factorization.

21405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1435.

The product of its (nonzero) digits is 40, while the sum is 12.

The square root of 21405 is about 146.3044770333. The cubic root of 21405 is about 27.7654730687.

Adding to 21405 its reverse (50412), we get a palindrome (71817).

It can be divided in two parts, 2140 and 5, that added together give a triangular number (2145 = T65).

The spelling of 21405 in words is "twenty-one thousand, four hundred five".

Divisors: 1 3 5 15 1427 4281 7135 21405