21753 has 6 divisors (see below), whose sum is σ = 31434. Its totient is φ = 14496.

The previous prime is 21751. The next prime is 21757. The reversal of 21753 is 35712.

It can be written as a sum of positive squares in only one way, i.e., 21609 + 144 = 147^2 + 12^2 .

It is not a de Polignac number, because 21753 - 2¹ = 21751 is a prime.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (21751) 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, 1200 + ... + 1217.

It is an arithmetic number, because the mean of its divisors is an integer number (5239).

21753 is a Friedman number, since it can be written as 7251*3, using all its digits and the basic arithmetic operations.

2²¹⁷⁵³ is an apocalyptic number.

It is an amenable number.

21753 is a deficient number, since it is larger than the sum of its proper divisors (9681).

21753 is a wasteful number, since it uses less digits than its factorization.

It is an anagram of its base 8 representation: 21753 = (52371)₈.

21753 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2423 (or 2420 counting only the distinct ones).

The product of its digits is 210, while the sum is 18.

The square root of 21753 is about 147.4889826394. The cubic root of 21753 is about 27.9151341947.

The spelling of 21753 in words is "twenty-one thousand, seven hundred fifty-three".