21675 has 18 divisors (see below), whose sum is σ = 38068. Its totient is φ = 10880.

The previous prime is 21673. The next prime is 21683. The reversal of 21675 is 57612.

It is not a de Polignac number, because 21675 - 2¹ = 21673 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (21673) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 1267 + ... + 1283.

2²¹⁶⁷⁵ is an apocalyptic number.

21675 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21675 is a deficient number, since it is larger than the sum of its proper divisors (16393).

21675 is a wasteful number, since it uses less digits than its factorization.

21675 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47 (or 25 counting only the distinct ones).

The product of its digits is 420, while the sum is 21.

The square root of 21675 is about 147.2243186434. The cubic root of 21675 is about 27.8817290223.

Subtracting 21675 from its reverse (57612), we obtain a cube (35937 = 33³).

It can be divided in two parts, 21 and 675, that added together give a palindrome (696).

The spelling of 21675 in words is "twenty-one thousand, six hundred seventy-five".