21321309 has 8 divisors (see below), whose sum is σ = 28704832. Its totient is φ = 14076000.

The previous prime is 21321301. The next prime is 21321331. The reversal of 21321309 is 90312312.

It is a happy number.

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

It is not a de Polignac number, because 21321309 - 2³ = 21321301 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 (21321301) 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 7 ways as a sum of consecutive naturals, for example, 34192 + ... + 34809.

It is an arithmetic number, because the mean of its divisors is an integer number (3588104).

Almost surely, 2^21321309 is an apocalyptic number.

It is an amenable number.

21321309 is a deficient number, since it is larger than the sum of its proper divisors (7383523).

21321309 is a wasteful number, since it uses less digits than its factorization.

21321309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69107.

The product of its (nonzero) digits is 324, while the sum is 21.

The square root of 21321309 is about 4617.5002977802. The cubic root of 21321309 is about 277.2923924029.

The spelling of 21321309 in words is "twenty-one million, three hundred twenty-one thousand, three hundred nine".