21205413 has 12 divisors (see below), whose sum is σ = 31282368. Its totient is φ = 13835880.

The previous prime is 21205399. The next prime is 21205447. The reversal of 21205413 is 31450212.

21205413 is a `hidden beast` number, since 2 + 120 + 541 + 3 = 666.

It is not a de Polignac number, because 21205413 - 2⁴ = 21205397 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205453) 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 11 ways as a sum of consecutive naturals, for example, 24643 + ... + 25488.

It is an arithmetic number, because the mean of its divisors is an integer number (2606864).

Almost surely, 2^21205413 is an apocalyptic number.

It is an amenable number.

21205413 is a deficient number, since it is larger than the sum of its proper divisors (10076955).

21205413 is a wasteful number, since it uses less digits than its factorization.

21205413 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50184 (or 50181 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21205413 is about 4604.9335500092. The cubic root of 21205413 is about 276.7890542535.

Adding to 21205413 its reverse (31450212), we get a palindrome (52655625).

The spelling of 21205413 in words is "twenty-one million, two hundred five thousand, four hundred thirteen".