21204351 has 12 divisors (see below), whose sum is σ = 35004112. Its totient is φ = 12116736.

The previous prime is 21204349. The next prime is 21204397. The reversal of 21204351 is 15340212.

It is not a de Polignac number, because 21204351 - 2¹ = 21204349 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 (21204251) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 168226 + ... + 168351.

Almost surely, 2^21204351 is an apocalyptic number.

21204351 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21204351 is a deficient number, since it is larger than the sum of its proper divisors (13799761).

21204351 is a wasteful number, since it uses less digits than its factorization.

21204351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 336590 (or 336587 counting only the distinct ones).

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

The square root of 21204351 is about 4604.8182374552. The cubic root of 21204351 is about 276.7844335012.

Adding to 21204351 its reverse (15340212), we get a palindrome (36544563).

The spelling of 21204351 in words is "twenty-one million, two hundred four thousand, three hundred fifty-one".