21453 has 4 divisors (see below), whose sum is σ = 28608. Its totient is φ = 14300.

The previous prime is 21433. The next prime is 21467. The reversal of 21453 is 35412.

21453 is nontrivially palindromic in base 8.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21453 is a prime.

It is a D-number.

21453 is a lucky number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21433) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3573 + ... + 3578.

It is an arithmetic number, because the mean of its divisors is an integer number (7152).

2²¹⁴⁵³ is an apocalyptic number.

It is an amenable number.

21453 is a deficient number, since it is larger than the sum of its proper divisors (7155).

21453 is an equidigital number, since it uses as much as digits as its factorization.

21453 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7154.

The product of its digits is 120, while the sum is 15.

The square root of 21453 is about 146.4684266318. The cubic root of 21453 is about 27.7862119574.

Adding to 21453 its reverse (35412), we get a palindrome (56865).

It can be divided in two parts, 21 and 453, that added together give a palindrome (474).

The spelling of 21453 in words is "twenty-one thousand, four hundred fifty-three".