21204613 has 4 divisors (see below), whose sum is σ = 21213900. Its totient is φ = 21195328.

The previous prime is 21204607. The next prime is 21204619. The reversal of 21204613 is 31640212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (21204607) and next prime (21204619).

It can be written as a sum of positive squares in 2 ways, for example, as 11950849 + 9253764 = 3457^2 + 3042^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21204613 is a prime.

It is a super-2 number, since 2×21204613² = 899271224959538, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21204619) 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, 1431 + ... + 6667.

It is an arithmetic number, because the mean of its divisors is an integer number (5303475).

Almost surely, 2^21204613 is an apocalyptic number.

It is an amenable number.

21204613 is a deficient number, since it is larger than the sum of its proper divisors (9287).

21204613 is an equidigital number, since it uses as much as digits as its factorization.

21204613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9286.

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21204613 is about 4604.8466858301. The cubic root of 21204613 is about 276.7855734752.

Adding to 21204613 its reverse (31640212), we get a palindrome (52844825).

The spelling of 21204613 in words is "twenty-one million, two hundred four thousand, six hundred thirteen".