21404351 has 4 divisors (see below), whose sum is σ = 21755304. Its totient is φ = 21053400.

The previous prime is 21404321. The next prime is 21404359. The reversal of 21404351 is 15340412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21404351 - 2²² = 17210047 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404359) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 175385 + ... + 175506.

It is an arithmetic number, because the mean of its divisors is an integer number (5438826).

Almost surely, 2^21404351 is an apocalyptic number.

21404351 is a deficient number, since it is larger than the sum of its proper divisors (350953).

21404351 is an equidigital number, since it uses as much as digits as its factorization.

21404351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350952.

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 21404351 is about 4626.4836539212. The cubic root of 21404351 is about 277.6519244932.

Adding to 21404351 its reverse (15340412), we get a palindrome (36744763).

The spelling of 21404351 in words is "twenty-one million, four hundred four thousand, three hundred fifty-one".