21313309 has 4 divisors (see below), whose sum is σ = 21323260. Its totient is φ = 21303360.

The previous prime is 21313301. The next prime is 21313333. The reversal of 21313309 is 90331312.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 3648100 + 17665209 = 1910^2 + 4203^2 .

It is a cyclic number.

It is not a de Polignac number, because 21313309 - 2³ = 21313301 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21313309.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21313301) 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, 294 + ... + 6535.

It is an arithmetic number, because the mean of its divisors is an integer number (5330815).

Almost surely, 2^21313309 is an apocalyptic number.

It is an amenable number.

21313309 is a deficient number, since it is larger than the sum of its proper divisors (9951).

21313309 is an equidigital number, since it uses as much as digits as its factorization.

21313309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9950.

The product of its (nonzero) digits is 486, while the sum is 22.

The square root of 21313309 is about 4616.6339469358. The cubic root of 21313309 is about 277.2577069677.

The spelling of 21313309 in words is "twenty-one million, three hundred thirteen thousand, three hundred nine".