21459205 has 4 divisors (see below), whose sum is σ = 25751052. Its totient is φ = 17167360.

The previous prime is 21459199. The next prime is 21459209. The reversal of 21459205 is 50295412.

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 10556001 + 10903204 = 3249^2 + 3302^2 .

It is not a de Polignac number, because 21459205 - 2³ = 21459197 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 (21459209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2145916 + ... + 2145925.

It is an arithmetic number, because the mean of its divisors is an integer number (6437763).

Almost surely, 2^21459205 is an apocalyptic number.

It is an amenable number.

21459205 is a deficient number, since it is larger than the sum of its proper divisors (4291847).

21459205 is an equidigital number, since it uses as much as digits as its factorization.

21459205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4291846.

The product of its (nonzero) digits is 3600, while the sum is 28.

The square root of 21459205 is about 4632.4081210532. The cubic root of 21459205 is about 277.8889063209. Note that the first 3 decimals are identical.

The spelling of 21459205 in words is "twenty-one million, four hundred fifty-nine thousand, two hundred five".