21331321 has 8 divisors (see below), whose sum is σ = 23415264. Its totient is φ = 19271520.

The previous prime is 21331313. The next prime is 21331333. The reversal of 21331321 is 12313312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21331321 - 2³ = 21331313 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21331295 and 21331304.

It is not an unprimeable number, because it can be changed into a prime (21331361) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4156 + ... + 7741.

It is an arithmetic number, because the mean of its divisors is an integer number (2926908).

Almost surely, 2^21331321 is an apocalyptic number.

It is an amenable number.

21331321 is a deficient number, since it is larger than the sum of its proper divisors (2083943).

21331321 is a wasteful number, since it uses less digits than its factorization.

21331321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12071.

The product of its digits is 108, while the sum is 16.

The square root of 21331321 is about 4618.5843069062. The cubic root of 21331321 is about 277.3357890035.

Adding to 21331321 its reverse (12313312), we get a palindrome (33644633).

Subtracting from 21331321 its reverse (12313312), we obtain a square (9018009 = 3003²).

The spelling of 21331321 in words is "twenty-one million, three hundred thirty-one thousand, three hundred twenty-one".