21853 has 6 divisors (see below), whose sum is σ = 24122. Its totient is φ = 19680.

The previous prime is 21851. The next prime is 21859. The reversal of 21853 is 35812.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 2809 + 19044 = 53^2 + 138^2 .

It is not a de Polignac number, because 21853 - 2¹ = 21851 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21853.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21851) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 513 + ... + 553.

2²¹⁸⁵³ is an apocalyptic number.

It is an amenable number.

21853 is a deficient number, since it is larger than the sum of its proper divisors (2269).

21853 is an equidigital number, since it uses as much as digits as its factorization.

21853 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95 (or 54 counting only the distinct ones).

The product of its digits is 240, while the sum is 19.

The square root of 21853 is about 147.8276022940. The cubic root of 21853 is about 27.9578447284.

It can be divided in two parts, 2185 and 3, that multiplied together give a triangular number (6555 = T₁₁₄).

The spelling of 21853 in words is "twenty-one thousand, eight hundred fifty-three".