Search a number
-
+
21615 = 3511131
BaseRepresentation
bin101010001101111
31002122120
411101233
51142430
6244023
7120006
oct52157
932576
1021615
1115270
1210613
139ab9
147c3d
156610
hex546f

21615 has 16 divisors (see below), whose sum is σ = 38016. Its totient is φ = 10400.

The previous prime is 21613. The next prime is 21617. The reversal of 21615 is 51612.

It is an interprime number because it is at equal distance from previous prime (21613) and next prime (21617).

It is not a de Polignac number, because 21615 - 21 = 21613 is a prime.

It is a Smith number, since the sum of its digits (15) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (15).

21615 is a lucky number.

It is a nialpdrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 21594 and 21603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21611) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 100 + ... + 230.

It is an arithmetic number, because the mean of its divisors is an integer number (2376).

221615 is an apocalyptic number.

21615 is a deficient number, since it is larger than the sum of its proper divisors (16401).

21615 is a wasteful number, since it uses less digits than its factorization.

21615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150.

The product of its digits is 60, while the sum is 15.

The square root of 21615 is about 147.0204067468. The cubic root of 21615 is about 27.8559781611.

21615 divided by its sum of digits (15) gives a palindrome (1441).

It can be divided in two parts, 216 and 15, that multiplied together give a triangular number (3240 = T80).

The spelling of 21615 in words is "twenty-one thousand, six hundred fifteen".

Divisors: 1 3 5 11 15 33 55 131 165 393 655 1441 1965 4323 7205 21615