21204317 has 4 divisors (see below), whose sum is σ = 21236316. Its totient is φ = 21172320.

The previous prime is 21204251. The next prime is 21204329. The reversal of 21204317 is 71340212.

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 17859076 + 3345241 = 4226^2 + 1829^2 .

It is a cyclic number.

It is not a de Polignac number, because 21204317 - 2¹⁰ = 21203293 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 (21204347) 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, 14984 + ... + 16337.

It is an arithmetic number, because the mean of its divisors is an integer number (5309079).

Almost surely, 2^21204317 is an apocalyptic number.

It is an amenable number.

21204317 is a deficient number, since it is larger than the sum of its proper divisors (31999).

21204317 is an equidigital number, since it uses as much as digits as its factorization.

21204317 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31998.

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 21204317 is about 4604.8145456685. The cubic root of 21204317 is about 276.7842855650.

Adding to 21204317 its reverse (71340212), we get a palindrome (92544529).

The spelling of 21204317 in words is "twenty-one million, two hundred four thousand, three hundred seventeen".