21885 has 8 divisors (see below), whose sum is σ = 35040. Its totient is φ = 11664.

The previous prime is 21881. The next prime is 21893. The reversal of 21885 is 58812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21885 - 2² = 21881 is a prime.

It is an Ulam number.

21885 is a lucky number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21881) 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, 715 + ... + 744.

It is an arithmetic number, because the mean of its divisors is an integer number (4380).

2²¹⁸⁸⁵ is an apocalyptic number.

It is an amenable number.

21885 is a deficient number, since it is larger than the sum of its proper divisors (13155).

21885 is a wasteful number, since it uses less digits than its factorization.

21885 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1467.

The product of its digits is 640, while the sum is 24.

The square root of 21885 is about 147.9357968850. The cubic root of 21885 is about 27.9714845750.

It can be divided in two parts, 218 and 85, that added together give a palindrome (303).

The spelling of 21885 in words is "twenty-one thousand, eight hundred eighty-five".