21453205 has 4 divisors (see below), whose sum is σ = 25743852. Its totient is φ = 17162560.

The previous prime is 21453203. The next prime is 21453239. The reversal of 21453205 is 50235412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16826404 + 4626801 = 4102^2 + 2151^2 .

It is not a de Polignac number, because 21453205 - 2¹ = 21453203 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21453203) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2145316 + ... + 2145325.

It is an arithmetic number, because the mean of its divisors is an integer number (6435963).

Almost surely, 2^21453205 is an apocalyptic number.

It is an amenable number.

21453205 is a deficient number, since it is larger than the sum of its proper divisors (4290647).

21453205 is an equidigital number, since it uses as much as digits as its factorization.

21453205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4290646.

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 21453205 is about 4631.7604644455. The cubic root of 21453205 is about 277.8630046335.

Adding to 21453205 its reverse (50235412), we get a palindrome (71688617).

The spelling of 21453205 in words is "twenty-one million, four hundred fifty-three thousand, two hundred five".